Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
the region") /dev/kmem zaps ptes when the kernel requests exclusive
acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
the default for all driver uses.
Except there's two more ways to access PCI BARs: sysfs and proc mmap
support. Let's plug that hole.
For revoke_devmem() to work we need to link our vma into the same
address_space, with consistent vma->vm_pgoff. ->pgoff is already
adjusted, because that's how (io_)remap_pfn_range works, but for the
mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
to adjust this at at ->open time:
- for sysfs this is easy, now that binary attributes support this. We
just set bin_attr->mapping when mmap is supported
- for procfs it's a bit more tricky, since procfs pci access has only
one file per device, and access to a specific resources first needs
to be set up with some ioctl calls. But mmap is only supported for
the same resources as sysfs exposes with mmap support, and otherwise
rejected, so we can set the mapping unconditionally at open time
without harm.
A special consideration is for arch_can_pci_mmap_io() - we need to
make sure that the ->f_mapping doesn't alias between ioport and iomem
space. There's only 2 ways in-tree to support mmap of ioports: generic
pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
architecture hand-rolling. Both approach support ioport mmap through a
special pfn range and not through magic pte attributes. Aliasing is
therefore not a problem.
The only difference in access checks left is that sysfs PCI mmap does
not check for CAP_RAWIO. I'm not really sure whether that should be
added or not.
Acked-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Bjorn Helgaas <[email protected]>
Cc: [email protected]
Signed-off-by: Daniel Vetter <[email protected]>
--
v2:
- Totally new approach: Adjust filp->f_mapping at open time. Note that
this now works on all architectures, not just those support
ARCH_GENERIC_PCI_MMAP_RESOURCE
---
drivers/pci/pci-sysfs.c | 4 ++++
drivers/pci/proc.c | 1 +
2 files changed, 5 insertions(+)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index d15c881e2e7e..3f1c31bc0b7c 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
b->legacy_io->read = pci_read_legacy_io;
b->legacy_io->write = pci_write_legacy_io;
b->legacy_io->mmap = pci_mmap_legacy_io;
+ b->legacy_io->mapping = iomem_get_mapping();
pci_adjust_legacy_attr(b, pci_mmap_io);
error = device_create_bin_file(&b->dev, b->legacy_io);
if (error)
@@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
b->legacy_mem->size = 1024*1024;
b->legacy_mem->attr.mode = 0600;
b->legacy_mem->mmap = pci_mmap_legacy_mem;
+ b->legacy_io->mapping = iomem_get_mapping();
pci_adjust_legacy_attr(b, pci_mmap_mem);
error = device_create_bin_file(&b->dev, b->legacy_mem);
if (error)
@@ -1156,6 +1158,8 @@ static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine)
res_attr->mmap = pci_mmap_resource_uc;
}
}
+ if (res_attr->mmap)
+ res_attr->mapping = iomem_get_mapping();
res_attr->attr.name = res_attr_name;
res_attr->attr.mode = 0600;
res_attr->size = pci_resource_len(pdev, num);
diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
index 3a2f90beb4cb..9bab07302bbf 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -298,6 +298,7 @@ static int proc_bus_pci_open(struct inode *inode, struct file *file)
fpriv->write_combine = 0;
file->private_data = fpriv;
+ file->f_mapping = iomem_get_mapping();
return 0;
}
--
2.29.2
On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
>
> Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> the region") /dev/kmem zaps ptes when the kernel requests exclusive
> acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> the default for all driver uses.
>
> Except there's two more ways to access PCI BARs: sysfs and proc mmap
> support. Let's plug that hole.
>
> For revoke_devmem() to work we need to link our vma into the same
> address_space, with consistent vma->vm_pgoff. ->pgoff is already
> adjusted, because that's how (io_)remap_pfn_range works, but for the
> mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> to adjust this at at ->open time:
>
> - for sysfs this is easy, now that binary attributes support this. We
> just set bin_attr->mapping when mmap is supported
> - for procfs it's a bit more tricky, since procfs pci access has only
> one file per device, and access to a specific resources first needs
> to be set up with some ioctl calls. But mmap is only supported for
> the same resources as sysfs exposes with mmap support, and otherwise
> rejected, so we can set the mapping unconditionally at open time
> without harm.
>
> A special consideration is for arch_can_pci_mmap_io() - we need to
> make sure that the ->f_mapping doesn't alias between ioport and iomem
> space. There's only 2 ways in-tree to support mmap of ioports: generic
> pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> architecture hand-rolling. Both approach support ioport mmap through a
> special pfn range and not through magic pte attributes. Aliasing is
> therefore not a problem.
>
> The only difference in access checks left is that sysfs PCI mmap does
> not check for CAP_RAWIO. I'm not really sure whether that should be
> added or not.
>
> Acked-by: Bjorn Helgaas <[email protected]>
> Reviewed-by: Dan Williams <[email protected]>
> Signed-off-by: Daniel Vetter <[email protected]>
> Cc: Jason Gunthorpe <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: John Hubbard <[email protected]>
> Cc: Jérôme Glisse <[email protected]>
> Cc: Jan Kara <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: Bjorn Helgaas <[email protected]>
> Cc: [email protected]
> Signed-off-by: Daniel Vetter <[email protected]>
> --
> v2:
> - Totally new approach: Adjust filp->f_mapping at open time. Note that
> this now works on all architectures, not just those support
> ARCH_GENERIC_PCI_MMAP_RESOURCE
> ---
> drivers/pci/pci-sysfs.c | 4 ++++
> drivers/pci/proc.c | 1 +
> 2 files changed, 5 insertions(+)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index d15c881e2e7e..3f1c31bc0b7c 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> b->legacy_io->read = pci_read_legacy_io;
> b->legacy_io->write = pci_write_legacy_io;
> b->legacy_io->mmap = pci_mmap_legacy_io;
> + b->legacy_io->mapping = iomem_get_mapping();
> pci_adjust_legacy_attr(b, pci_mmap_io);
> error = device_create_bin_file(&b->dev, b->legacy_io);
> if (error)
> @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> b->legacy_mem->size = 1024*1024;
> b->legacy_mem->attr.mode = 0600;
> b->legacy_mem->mmap = pci_mmap_legacy_mem;
> + b->legacy_io->mapping = iomem_get_mapping();
Unlike the normal pci stuff below, the legacy files here go boom
because they're set up much earlier in the boot sequence. This only
affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
should we do here now:
- drop the devmem revoke for these
- rework the init sequence somehow to set up these files a lot later
- redo the sysfs patch so that it doesn't take an address_space
pointer, but instead a callback to get at that (since at open time
everything is set up). Imo rather ugly
- ditch this part of the series (since there's not really any takers
for the latter parts it might just not make sense to push for this)
- something else?
Bjorn, Greg, thoughts?
Issuge got reported by Stephen on a powerpc when trying to build
linux-next with this patch included.
Thanks, Daniel
> pci_adjust_legacy_attr(b, pci_mmap_mem);
> error = device_create_bin_file(&b->dev, b->legacy_mem);
> if (error)
> @@ -1156,6 +1158,8 @@ static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine)
> res_attr->mmap = pci_mmap_resource_uc;
> }
> }
> + if (res_attr->mmap)
> + res_attr->mapping = iomem_get_mapping();
> res_attr->attr.name = res_attr_name;
> res_attr->attr.mode = 0600;
> res_attr->size = pci_resource_len(pdev, num);
> diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
> index 3a2f90beb4cb..9bab07302bbf 100644
> --- a/drivers/pci/proc.c
> +++ b/drivers/pci/proc.c
> @@ -298,6 +298,7 @@ static int proc_bus_pci_open(struct inode *inode, struct file *file)
> fpriv->write_combine = 0;
>
> file->private_data = fpriv;
> + file->f_mapping = iomem_get_mapping();
>
> return 0;
> }
> --
> 2.29.2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Tue, Jan 19, 2021 at 03:34:47PM +0100, Daniel Vetter wrote:
> On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman
> <[email protected]> wrote:
> >
> > On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> > > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> > > >
> > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > > > the default for all driver uses.
> > > >
> > > > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > > > support. Let's plug that hole.
> > > >
> > > > For revoke_devmem() to work we need to link our vma into the same
> > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > > > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > > > to adjust this at at ->open time:
> > > >
> > > > - for sysfs this is easy, now that binary attributes support this. We
> > > > just set bin_attr->mapping when mmap is supported
> > > > - for procfs it's a bit more tricky, since procfs pci access has only
> > > > one file per device, and access to a specific resources first needs
> > > > to be set up with some ioctl calls. But mmap is only supported for
> > > > the same resources as sysfs exposes with mmap support, and otherwise
> > > > rejected, so we can set the mapping unconditionally at open time
> > > > without harm.
> > > >
> > > > A special consideration is for arch_can_pci_mmap_io() - we need to
> > > > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > > > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > > > architecture hand-rolling. Both approach support ioport mmap through a
> > > > special pfn range and not through magic pte attributes. Aliasing is
> > > > therefore not a problem.
> > > >
> > > > The only difference in access checks left is that sysfs PCI mmap does
> > > > not check for CAP_RAWIO. I'm not really sure whether that should be
> > > > added or not.
> > > >
> > > > Acked-by: Bjorn Helgaas <[email protected]>
> > > > Reviewed-by: Dan Williams <[email protected]>
> > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > Cc: Jason Gunthorpe <[email protected]>
> > > > Cc: Kees Cook <[email protected]>
> > > > Cc: Dan Williams <[email protected]>
> > > > Cc: Andrew Morton <[email protected]>
> > > > Cc: John Hubbard <[email protected]>
> > > > Cc: J?r?me Glisse <[email protected]>
> > > > Cc: Jan Kara <[email protected]>
> > > > Cc: Dan Williams <[email protected]>
> > > > Cc: Greg Kroah-Hartman <[email protected]>
> > > > Cc: [email protected]
> > > > Cc: [email protected]
> > > > Cc: [email protected]
> > > > Cc: [email protected]
> > > > Cc: Bjorn Helgaas <[email protected]>
> > > > Cc: [email protected]
> > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > --
> > > > v2:
> > > > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > > > this now works on all architectures, not just those support
> > > > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > > > ---
> > > > drivers/pci/pci-sysfs.c | 4 ++++
> > > > drivers/pci/proc.c | 1 +
> > > > 2 files changed, 5 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > > > index d15c881e2e7e..3f1c31bc0b7c 100644
> > > > --- a/drivers/pci/pci-sysfs.c
> > > > +++ b/drivers/pci/pci-sysfs.c
> > > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > b->legacy_io->read = pci_read_legacy_io;
> > > > b->legacy_io->write = pci_write_legacy_io;
> > > > b->legacy_io->mmap = pci_mmap_legacy_io;
> > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > pci_adjust_legacy_attr(b, pci_mmap_io);
> > > > error = device_create_bin_file(&b->dev, b->legacy_io);
> > > > if (error)
> > > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > b->legacy_mem->size = 1024*1024;
> > > > b->legacy_mem->attr.mode = 0600;
> > > > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > > > + b->legacy_io->mapping = iomem_get_mapping();
> > >
> > > Unlike the normal pci stuff below, the legacy files here go boom
> > > because they're set up much earlier in the boot sequence. This only
> > > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> > > should we do here now:
> > > - drop the devmem revoke for these
> > > - rework the init sequence somehow to set up these files a lot later
> > > - redo the sysfs patch so that it doesn't take an address_space
> > > pointer, but instead a callback to get at that (since at open time
> > > everything is set up). Imo rather ugly
> > > - ditch this part of the series (since there's not really any takers
> > > for the latter parts it might just not make sense to push for this)
> > > - something else?
> > >
> > > Bjorn, Greg, thoughts?
> >
> > What sysfs patch are you referring to here?
>
> Currently in linux-next:
>
> commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD ->
> topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup)
> Author: Daniel Vetter <[email protected]>
> Date: Fri Nov 27 17:41:25 2020 +0100
>
> sysfs: Support zapping of binary attr mmaps
>
> Or the patch right before this one in this submission here:
>
> https://lore.kernel.org/dri-devel/[email protected]/
Ah. Hm, a callback in the sysfs file logic seems really hairy, so I
would prefer that not happen. If no one really needs this stuff, why
not just drop it like you mention?
thanks,
greg k-h
On Tue, Jan 19, 2021 at 4:20 PM Greg Kroah-Hartman
<[email protected]> wrote:
>
> On Tue, Jan 19, 2021 at 03:34:47PM +0100, Daniel Vetter wrote:
> > On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman
> > <[email protected]> wrote:
> > >
> > > On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> > > > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> > > > >
> > > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > > > > the default for all driver uses.
> > > > >
> > > > > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > > > > support. Let's plug that hole.
> > > > >
> > > > > For revoke_devmem() to work we need to link our vma into the same
> > > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > > > > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > > > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > > > > to adjust this at at ->open time:
> > > > >
> > > > > - for sysfs this is easy, now that binary attributes support this. We
> > > > > just set bin_attr->mapping when mmap is supported
> > > > > - for procfs it's a bit more tricky, since procfs pci access has only
> > > > > one file per device, and access to a specific resources first needs
> > > > > to be set up with some ioctl calls. But mmap is only supported for
> > > > > the same resources as sysfs exposes with mmap support, and otherwise
> > > > > rejected, so we can set the mapping unconditionally at open time
> > > > > without harm.
> > > > >
> > > > > A special consideration is for arch_can_pci_mmap_io() - we need to
> > > > > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > > > > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > > > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > > > > architecture hand-rolling. Both approach support ioport mmap through a
> > > > > special pfn range and not through magic pte attributes. Aliasing is
> > > > > therefore not a problem.
> > > > >
> > > > > The only difference in access checks left is that sysfs PCI mmap does
> > > > > not check for CAP_RAWIO. I'm not really sure whether that should be
> > > > > added or not.
> > > > >
> > > > > Acked-by: Bjorn Helgaas <[email protected]>
> > > > > Reviewed-by: Dan Williams <[email protected]>
> > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > Cc: Jason Gunthorpe <[email protected]>
> > > > > Cc: Kees Cook <[email protected]>
> > > > > Cc: Dan Williams <[email protected]>
> > > > > Cc: Andrew Morton <[email protected]>
> > > > > Cc: John Hubbard <[email protected]>
> > > > > Cc: Jérôme Glisse <[email protected]>
> > > > > Cc: Jan Kara <[email protected]>
> > > > > Cc: Dan Williams <[email protected]>
> > > > > Cc: Greg Kroah-Hartman <[email protected]>
> > > > > Cc: [email protected]
> > > > > Cc: [email protected]
> > > > > Cc: [email protected]
> > > > > Cc: [email protected]
> > > > > Cc: Bjorn Helgaas <[email protected]>
> > > > > Cc: [email protected]
> > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > --
> > > > > v2:
> > > > > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > > > > this now works on all architectures, not just those support
> > > > > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > > > > ---
> > > > > drivers/pci/pci-sysfs.c | 4 ++++
> > > > > drivers/pci/proc.c | 1 +
> > > > > 2 files changed, 5 insertions(+)
> > > > >
> > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > > > > index d15c881e2e7e..3f1c31bc0b7c 100644
> > > > > --- a/drivers/pci/pci-sysfs.c
> > > > > +++ b/drivers/pci/pci-sysfs.c
> > > > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > b->legacy_io->read = pci_read_legacy_io;
> > > > > b->legacy_io->write = pci_write_legacy_io;
> > > > > b->legacy_io->mmap = pci_mmap_legacy_io;
> > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > > pci_adjust_legacy_attr(b, pci_mmap_io);
> > > > > error = device_create_bin_file(&b->dev, b->legacy_io);
> > > > > if (error)
> > > > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > b->legacy_mem->size = 1024*1024;
> > > > > b->legacy_mem->attr.mode = 0600;
> > > > > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > >
> > > > Unlike the normal pci stuff below, the legacy files here go boom
> > > > because they're set up much earlier in the boot sequence. This only
> > > > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> > > > should we do here now:
> > > > - drop the devmem revoke for these
> > > > - rework the init sequence somehow to set up these files a lot later
> > > > - redo the sysfs patch so that it doesn't take an address_space
> > > > pointer, but instead a callback to get at that (since at open time
> > > > everything is set up). Imo rather ugly
> > > > - ditch this part of the series (since there's not really any takers
> > > > for the latter parts it might just not make sense to push for this)
> > > > - something else?
> > > >
> > > > Bjorn, Greg, thoughts?
> > >
> > > What sysfs patch are you referring to here?
> >
> > Currently in linux-next:
> >
> > commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD ->
> > topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup)
> > Author: Daniel Vetter <[email protected]>
> > Date: Fri Nov 27 17:41:25 2020 +0100
> >
> > sysfs: Support zapping of binary attr mmaps
> >
> > Or the patch right before this one in this submission here:
> >
> > https://lore.kernel.org/dri-devel/[email protected]/
>
> Ah. Hm, a callback in the sysfs file logic seems really hairy, so I
> would prefer that not happen. If no one really needs this stuff, why
> not just drop it like you mention?
Well it is needed, but just on architectures I don't care about much.
Most relevant is perhaps powerpc (that's where Stephen hit the issue).
I do wonder whether we could move the legacy pci files setup to where
the modern stuff is set up from pci_create_resource_files() or maybe
pci_create_sysfs_dev_files() even for HAVE_PCI_LEGACY. I think that
might work, but since it's legacy flow on some funny architectures
(alpha, itanium, that kind of stuff) I have no idea what kind of
monsters I'm going to anger :-)
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman
<[email protected]> wrote:
>
> On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> > >
> > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > > the default for all driver uses.
> > >
> > > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > > support. Let's plug that hole.
> > >
> > > For revoke_devmem() to work we need to link our vma into the same
> > > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > > to adjust this at at ->open time:
> > >
> > > - for sysfs this is easy, now that binary attributes support this. We
> > > just set bin_attr->mapping when mmap is supported
> > > - for procfs it's a bit more tricky, since procfs pci access has only
> > > one file per device, and access to a specific resources first needs
> > > to be set up with some ioctl calls. But mmap is only supported for
> > > the same resources as sysfs exposes with mmap support, and otherwise
> > > rejected, so we can set the mapping unconditionally at open time
> > > without harm.
> > >
> > > A special consideration is for arch_can_pci_mmap_io() - we need to
> > > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > > architecture hand-rolling. Both approach support ioport mmap through a
> > > special pfn range and not through magic pte attributes. Aliasing is
> > > therefore not a problem.
> > >
> > > The only difference in access checks left is that sysfs PCI mmap does
> > > not check for CAP_RAWIO. I'm not really sure whether that should be
> > > added or not.
> > >
> > > Acked-by: Bjorn Helgaas <[email protected]>
> > > Reviewed-by: Dan Williams <[email protected]>
> > > Signed-off-by: Daniel Vetter <[email protected]>
> > > Cc: Jason Gunthorpe <[email protected]>
> > > Cc: Kees Cook <[email protected]>
> > > Cc: Dan Williams <[email protected]>
> > > Cc: Andrew Morton <[email protected]>
> > > Cc: John Hubbard <[email protected]>
> > > Cc: Jérôme Glisse <[email protected]>
> > > Cc: Jan Kara <[email protected]>
> > > Cc: Dan Williams <[email protected]>
> > > Cc: Greg Kroah-Hartman <[email protected]>
> > > Cc: [email protected]
> > > Cc: [email protected]
> > > Cc: [email protected]
> > > Cc: [email protected]
> > > Cc: Bjorn Helgaas <[email protected]>
> > > Cc: [email protected]
> > > Signed-off-by: Daniel Vetter <[email protected]>
> > > --
> > > v2:
> > > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > > this now works on all architectures, not just those support
> > > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > > ---
> > > drivers/pci/pci-sysfs.c | 4 ++++
> > > drivers/pci/proc.c | 1 +
> > > 2 files changed, 5 insertions(+)
> > >
> > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > > index d15c881e2e7e..3f1c31bc0b7c 100644
> > > --- a/drivers/pci/pci-sysfs.c
> > > +++ b/drivers/pci/pci-sysfs.c
> > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > b->legacy_io->read = pci_read_legacy_io;
> > > b->legacy_io->write = pci_write_legacy_io;
> > > b->legacy_io->mmap = pci_mmap_legacy_io;
> > > + b->legacy_io->mapping = iomem_get_mapping();
> > > pci_adjust_legacy_attr(b, pci_mmap_io);
> > > error = device_create_bin_file(&b->dev, b->legacy_io);
> > > if (error)
> > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > b->legacy_mem->size = 1024*1024;
> > > b->legacy_mem->attr.mode = 0600;
> > > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > > + b->legacy_io->mapping = iomem_get_mapping();
> >
> > Unlike the normal pci stuff below, the legacy files here go boom
> > because they're set up much earlier in the boot sequence. This only
> > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> > should we do here now:
> > - drop the devmem revoke for these
> > - rework the init sequence somehow to set up these files a lot later
> > - redo the sysfs patch so that it doesn't take an address_space
> > pointer, but instead a callback to get at that (since at open time
> > everything is set up). Imo rather ugly
> > - ditch this part of the series (since there's not really any takers
> > for the latter parts it might just not make sense to push for this)
> > - something else?
> >
> > Bjorn, Greg, thoughts?
>
> What sysfs patch are you referring to here?
Currently in linux-next:
commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD ->
topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup)
Author: Daniel Vetter <[email protected]>
Date: Fri Nov 27 17:41:25 2020 +0100
sysfs: Support zapping of binary attr mmaps
Or the patch right before this one in this submission here:
https://lore.kernel.org/dri-devel/[email protected]/
Cheers, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> >
> > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > the default for all driver uses.
> >
> > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > support. Let's plug that hole.
> >
> > For revoke_devmem() to work we need to link our vma into the same
> > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > to adjust this at at ->open time:
> >
> > - for sysfs this is easy, now that binary attributes support this. We
> > just set bin_attr->mapping when mmap is supported
> > - for procfs it's a bit more tricky, since procfs pci access has only
> > one file per device, and access to a specific resources first needs
> > to be set up with some ioctl calls. But mmap is only supported for
> > the same resources as sysfs exposes with mmap support, and otherwise
> > rejected, so we can set the mapping unconditionally at open time
> > without harm.
> >
> > A special consideration is for arch_can_pci_mmap_io() - we need to
> > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > architecture hand-rolling. Both approach support ioport mmap through a
> > special pfn range and not through magic pte attributes. Aliasing is
> > therefore not a problem.
> >
> > The only difference in access checks left is that sysfs PCI mmap does
> > not check for CAP_RAWIO. I'm not really sure whether that should be
> > added or not.
> >
> > Acked-by: Bjorn Helgaas <[email protected]>
> > Reviewed-by: Dan Williams <[email protected]>
> > Signed-off-by: Daniel Vetter <[email protected]>
> > Cc: Jason Gunthorpe <[email protected]>
> > Cc: Kees Cook <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: Andrew Morton <[email protected]>
> > Cc: John Hubbard <[email protected]>
> > Cc: J?r?me Glisse <[email protected]>
> > Cc: Jan Kara <[email protected]>
> > Cc: Dan Williams <[email protected]>
> > Cc: Greg Kroah-Hartman <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: Bjorn Helgaas <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Daniel Vetter <[email protected]>
> > --
> > v2:
> > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > this now works on all architectures, not just those support
> > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > ---
> > drivers/pci/pci-sysfs.c | 4 ++++
> > drivers/pci/proc.c | 1 +
> > 2 files changed, 5 insertions(+)
> >
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index d15c881e2e7e..3f1c31bc0b7c 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > b->legacy_io->read = pci_read_legacy_io;
> > b->legacy_io->write = pci_write_legacy_io;
> > b->legacy_io->mmap = pci_mmap_legacy_io;
> > + b->legacy_io->mapping = iomem_get_mapping();
> > pci_adjust_legacy_attr(b, pci_mmap_io);
> > error = device_create_bin_file(&b->dev, b->legacy_io);
> > if (error)
> > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > b->legacy_mem->size = 1024*1024;
> > b->legacy_mem->attr.mode = 0600;
> > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > + b->legacy_io->mapping = iomem_get_mapping();
>
> Unlike the normal pci stuff below, the legacy files here go boom
> because they're set up much earlier in the boot sequence. This only
> affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> should we do here now:
> - drop the devmem revoke for these
> - rework the init sequence somehow to set up these files a lot later
> - redo the sysfs patch so that it doesn't take an address_space
> pointer, but instead a callback to get at that (since at open time
> everything is set up). Imo rather ugly
> - ditch this part of the series (since there's not really any takers
> for the latter parts it might just not make sense to push for this)
> - something else?
>
> Bjorn, Greg, thoughts?
What sysfs patch are you referring to here?
thanks,
greg k-h
On Tue, Jan 19, 2021 at 5:03 PM Daniel Vetter <[email protected]> wrote:
>
> On Tue, Jan 19, 2021 at 4:20 PM Greg Kroah-Hartman
> <[email protected]> wrote:
> >
> > On Tue, Jan 19, 2021 at 03:34:47PM +0100, Daniel Vetter wrote:
> > > On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman
> > > <[email protected]> wrote:
> > > >
> > > > On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> > > > > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> > > > > >
> > > > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > > > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > > > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > > > > > the default for all driver uses.
> > > > > >
> > > > > > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > > > > > support. Let's plug that hole.
> > > > > >
> > > > > > For revoke_devmem() to work we need to link our vma into the same
> > > > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > > > > > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > > > > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > > > > > to adjust this at at ->open time:
> > > > > >
> > > > > > - for sysfs this is easy, now that binary attributes support this. We
> > > > > > just set bin_attr->mapping when mmap is supported
> > > > > > - for procfs it's a bit more tricky, since procfs pci access has only
> > > > > > one file per device, and access to a specific resources first needs
> > > > > > to be set up with some ioctl calls. But mmap is only supported for
> > > > > > the same resources as sysfs exposes with mmap support, and otherwise
> > > > > > rejected, so we can set the mapping unconditionally at open time
> > > > > > without harm.
> > > > > >
> > > > > > A special consideration is for arch_can_pci_mmap_io() - we need to
> > > > > > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > > > > > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > > > > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > > > > > architecture hand-rolling. Both approach support ioport mmap through a
> > > > > > special pfn range and not through magic pte attributes. Aliasing is
> > > > > > therefore not a problem.
> > > > > >
> > > > > > The only difference in access checks left is that sysfs PCI mmap does
> > > > > > not check for CAP_RAWIO. I'm not really sure whether that should be
> > > > > > added or not.
> > > > > >
> > > > > > Acked-by: Bjorn Helgaas <[email protected]>
> > > > > > Reviewed-by: Dan Williams <[email protected]>
> > > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > > Cc: Jason Gunthorpe <[email protected]>
> > > > > > Cc: Kees Cook <[email protected]>
> > > > > > Cc: Dan Williams <[email protected]>
> > > > > > Cc: Andrew Morton <[email protected]>
> > > > > > Cc: John Hubbard <[email protected]>
> > > > > > Cc: Jérôme Glisse <[email protected]>
> > > > > > Cc: Jan Kara <[email protected]>
> > > > > > Cc: Dan Williams <[email protected]>
> > > > > > Cc: Greg Kroah-Hartman <[email protected]>
> > > > > > Cc: [email protected]
> > > > > > Cc: [email protected]
> > > > > > Cc: [email protected]
> > > > > > Cc: [email protected]
> > > > > > Cc: Bjorn Helgaas <[email protected]>
> > > > > > Cc: [email protected]
> > > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > > --
> > > > > > v2:
> > > > > > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > > > > > this now works on all architectures, not just those support
> > > > > > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > > > > > ---
> > > > > > drivers/pci/pci-sysfs.c | 4 ++++
> > > > > > drivers/pci/proc.c | 1 +
> > > > > > 2 files changed, 5 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > > > > > index d15c881e2e7e..3f1c31bc0b7c 100644
> > > > > > --- a/drivers/pci/pci-sysfs.c
> > > > > > +++ b/drivers/pci/pci-sysfs.c
> > > > > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > > b->legacy_io->read = pci_read_legacy_io;
> > > > > > b->legacy_io->write = pci_write_legacy_io;
> > > > > > b->legacy_io->mmap = pci_mmap_legacy_io;
> > > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > > > pci_adjust_legacy_attr(b, pci_mmap_io);
> > > > > > error = device_create_bin_file(&b->dev, b->legacy_io);
> > > > > > if (error)
> > > > > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > > b->legacy_mem->size = 1024*1024;
> > > > > > b->legacy_mem->attr.mode = 0600;
> > > > > > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > >
> > > > > Unlike the normal pci stuff below, the legacy files here go boom
> > > > > because they're set up much earlier in the boot sequence. This only
> > > > > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> > > > > should we do here now:
> > > > > - drop the devmem revoke for these
> > > > > - rework the init sequence somehow to set up these files a lot later
> > > > > - redo the sysfs patch so that it doesn't take an address_space
> > > > > pointer, but instead a callback to get at that (since at open time
> > > > > everything is set up). Imo rather ugly
> > > > > - ditch this part of the series (since there's not really any takers
> > > > > for the latter parts it might just not make sense to push for this)
> > > > > - something else?
> > > > >
> > > > > Bjorn, Greg, thoughts?
> > > >
> > > > What sysfs patch are you referring to here?
> > >
> > > Currently in linux-next:
> > >
> > > commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD ->
> > > topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup)
> > > Author: Daniel Vetter <[email protected]>
> > > Date: Fri Nov 27 17:41:25 2020 +0100
> > >
> > > sysfs: Support zapping of binary attr mmaps
> > >
> > > Or the patch right before this one in this submission here:
> > >
> > > https://lore.kernel.org/dri-devel/[email protected]/
> >
> > Ah. Hm, a callback in the sysfs file logic seems really hairy, so I
> > would prefer that not happen. If no one really needs this stuff, why
> > not just drop it like you mention?
>
> Well it is needed, but just on architectures I don't care about much.
> Most relevant is perhaps powerpc (that's where Stephen hit the issue).
> I do wonder whether we could move the legacy pci files setup to where
> the modern stuff is set up from pci_create_resource_files() or maybe
> pci_create_sysfs_dev_files() even for HAVE_PCI_LEGACY. I think that
> might work, but since it's legacy flow on some funny architectures
> (alpha, itanium, that kind of stuff) I have no idea what kind of
> monsters I'm going to anger :-)
Back from a week of vacation, I looked at this again and I think
shouldn't be hard to fix this with the sam trick
pci_create_sysfs_dev_files() uses: As long as sysfs_initialized isn't
set we skip, and then later on when the vfs is up&running we can
initialize everything.
To be able to apply the same thing to pci_create_legacy_files() I
think all I need is to iterate overa all struct pci_bus in
pci_sysfs_init() and we're good. Unfortunately I didn't find any
for_each_pci_bus(), so how do I do that?
Thanks, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
On Wed, Feb 3, 2021 at 5:14 PM Daniel Vetter <[email protected]> wrote:
>
> On Tue, Jan 19, 2021 at 5:03 PM Daniel Vetter <[email protected]> wrote:
> >
> > On Tue, Jan 19, 2021 at 4:20 PM Greg Kroah-Hartman
> > <[email protected]> wrote:
> > >
> > > On Tue, Jan 19, 2021 at 03:34:47PM +0100, Daniel Vetter wrote:
> > > > On Tue, Jan 19, 2021 at 3:32 PM Greg Kroah-Hartman
> > > > <[email protected]> wrote:
> > > > >
> > > > > On Tue, Jan 19, 2021 at 09:17:55AM +0100, Daniel Vetter wrote:
> > > > > > On Fri, Nov 27, 2020 at 5:42 PM Daniel Vetter <[email protected]> wrote:
> > > > > > >
> > > > > > > Since 3234ac664a87 ("/dev/mem: Revoke mappings when a driver claims
> > > > > > > the region") /dev/kmem zaps ptes when the kernel requests exclusive
> > > > > > > acccess to an iomem region. And with CONFIG_IO_STRICT_DEVMEM, this is
> > > > > > > the default for all driver uses.
> > > > > > >
> > > > > > > Except there's two more ways to access PCI BARs: sysfs and proc mmap
> > > > > > > support. Let's plug that hole.
> > > > > > >
> > > > > > > For revoke_devmem() to work we need to link our vma into the same
> > > > > > > address_space, with consistent vma->vm_pgoff. ->pgoff is already
> > > > > > > adjusted, because that's how (io_)remap_pfn_range works, but for the
> > > > > > > mapping we need to adjust vma->vm_file->f_mapping. The cleanest way is
> > > > > > > to adjust this at at ->open time:
> > > > > > >
> > > > > > > - for sysfs this is easy, now that binary attributes support this. We
> > > > > > > just set bin_attr->mapping when mmap is supported
> > > > > > > - for procfs it's a bit more tricky, since procfs pci access has only
> > > > > > > one file per device, and access to a specific resources first needs
> > > > > > > to be set up with some ioctl calls. But mmap is only supported for
> > > > > > > the same resources as sysfs exposes with mmap support, and otherwise
> > > > > > > rejected, so we can set the mapping unconditionally at open time
> > > > > > > without harm.
> > > > > > >
> > > > > > > A special consideration is for arch_can_pci_mmap_io() - we need to
> > > > > > > make sure that the ->f_mapping doesn't alias between ioport and iomem
> > > > > > > space. There's only 2 ways in-tree to support mmap of ioports: generic
> > > > > > > pci mmap (ARCH_GENERIC_PCI_MMAP_RESOURCE), and sparc as the single
> > > > > > > architecture hand-rolling. Both approach support ioport mmap through a
> > > > > > > special pfn range and not through magic pte attributes. Aliasing is
> > > > > > > therefore not a problem.
> > > > > > >
> > > > > > > The only difference in access checks left is that sysfs PCI mmap does
> > > > > > > not check for CAP_RAWIO. I'm not really sure whether that should be
> > > > > > > added or not.
> > > > > > >
> > > > > > > Acked-by: Bjorn Helgaas <[email protected]>
> > > > > > > Reviewed-by: Dan Williams <[email protected]>
> > > > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > > > Cc: Jason Gunthorpe <[email protected]>
> > > > > > > Cc: Kees Cook <[email protected]>
> > > > > > > Cc: Dan Williams <[email protected]>
> > > > > > > Cc: Andrew Morton <[email protected]>
> > > > > > > Cc: John Hubbard <[email protected]>
> > > > > > > Cc: Jérôme Glisse <[email protected]>
> > > > > > > Cc: Jan Kara <[email protected]>
> > > > > > > Cc: Dan Williams <[email protected]>
> > > > > > > Cc: Greg Kroah-Hartman <[email protected]>
> > > > > > > Cc: [email protected]
> > > > > > > Cc: [email protected]
> > > > > > > Cc: [email protected]
> > > > > > > Cc: [email protected]
> > > > > > > Cc: Bjorn Helgaas <[email protected]>
> > > > > > > Cc: [email protected]
> > > > > > > Signed-off-by: Daniel Vetter <[email protected]>
> > > > > > > --
> > > > > > > v2:
> > > > > > > - Totally new approach: Adjust filp->f_mapping at open time. Note that
> > > > > > > this now works on all architectures, not just those support
> > > > > > > ARCH_GENERIC_PCI_MMAP_RESOURCE
> > > > > > > ---
> > > > > > > drivers/pci/pci-sysfs.c | 4 ++++
> > > > > > > drivers/pci/proc.c | 1 +
> > > > > > > 2 files changed, 5 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > > > > > > index d15c881e2e7e..3f1c31bc0b7c 100644
> > > > > > > --- a/drivers/pci/pci-sysfs.c
> > > > > > > +++ b/drivers/pci/pci-sysfs.c
> > > > > > > @@ -929,6 +929,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > > > b->legacy_io->read = pci_read_legacy_io;
> > > > > > > b->legacy_io->write = pci_write_legacy_io;
> > > > > > > b->legacy_io->mmap = pci_mmap_legacy_io;
> > > > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > > > > pci_adjust_legacy_attr(b, pci_mmap_io);
> > > > > > > error = device_create_bin_file(&b->dev, b->legacy_io);
> > > > > > > if (error)
> > > > > > > @@ -941,6 +942,7 @@ void pci_create_legacy_files(struct pci_bus *b)
> > > > > > > b->legacy_mem->size = 1024*1024;
> > > > > > > b->legacy_mem->attr.mode = 0600;
> > > > > > > b->legacy_mem->mmap = pci_mmap_legacy_mem;
> > > > > > > + b->legacy_io->mapping = iomem_get_mapping();
> > > > > >
> > > > > > Unlike the normal pci stuff below, the legacy files here go boom
> > > > > > because they're set up much earlier in the boot sequence. This only
> > > > > > affects HAVE_PCI_LEGACY architectures, which aren't that many. So what
> > > > > > should we do here now:
> > > > > > - drop the devmem revoke for these
> > > > > > - rework the init sequence somehow to set up these files a lot later
> > > > > > - redo the sysfs patch so that it doesn't take an address_space
> > > > > > pointer, but instead a callback to get at that (since at open time
> > > > > > everything is set up). Imo rather ugly
> > > > > > - ditch this part of the series (since there's not really any takers
> > > > > > for the latter parts it might just not make sense to push for this)
> > > > > > - something else?
> > > > > >
> > > > > > Bjorn, Greg, thoughts?
> > > > >
> > > > > What sysfs patch are you referring to here?
> > > >
> > > > Currently in linux-next:
> > > >
> > > > commit 74b30195395c406c787280a77ae55aed82dbbfc7 (HEAD ->
> > > > topic/iomem-mmap-vs-gup, drm/topic/iomem-mmap-vs-gup)
> > > > Author: Daniel Vetter <[email protected]>
> > > > Date: Fri Nov 27 17:41:25 2020 +0100
> > > >
> > > > sysfs: Support zapping of binary attr mmaps
> > > >
> > > > Or the patch right before this one in this submission here:
> > > >
> > > > https://lore.kernel.org/dri-devel/[email protected]/
> > >
> > > Ah. Hm, a callback in the sysfs file logic seems really hairy, so I
> > > would prefer that not happen. If no one really needs this stuff, why
> > > not just drop it like you mention?
> >
> > Well it is needed, but just on architectures I don't care about much.
> > Most relevant is perhaps powerpc (that's where Stephen hit the issue).
> > I do wonder whether we could move the legacy pci files setup to where
> > the modern stuff is set up from pci_create_resource_files() or maybe
> > pci_create_sysfs_dev_files() even for HAVE_PCI_LEGACY. I think that
> > might work, but since it's legacy flow on some funny architectures
> > (alpha, itanium, that kind of stuff) I have no idea what kind of
> > monsters I'm going to anger :-)
>
> Back from a week of vacation, I looked at this again and I think
> shouldn't be hard to fix this with the sam trick
> pci_create_sysfs_dev_files() uses: As long as sysfs_initialized isn't
> set we skip, and then later on when the vfs is up&running we can
> initialize everything.
>
> To be able to apply the same thing to pci_create_legacy_files() I
> think all I need is to iterate overa all struct pci_bus in
> pci_sysfs_init() and we're good. Unfortunately I didn't find any
> for_each_pci_bus(), so how do I do that?
pci_find_next_bus() seems to be the answer I want. I'll see whether
that works and then send out new patches.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch