2021-02-06 00:08:02

by Daniel Vetter

Subject: [PATCH] PCI: Also set up legacy files only after sysfs init

We are already doing this for all the regular sysfs files on PCI
devices, but not yet on the legacy io files on the PCI buses. Thus far
no problem, but in the next patch I want to wire up iomem revoke
support. That needs the vfs up and running already to make sure that
iomem_get_mapping() works.

Wire it up exactly like the existing code in
pci_create_sysfs_dev_files(). Note that pci_remove_legacy_files()
doesn't need a check since the one for pci_bus->legacy_io is
sufficient.

An alternative solution would be to implement a callback in sysfs to
set up the address space from iomem_get_mapping() when userspace calls
mmap(). This also works, but Greg didn't really like that just to work
around an ordering issue when the kernel loads initially.

v2: Improve commit message (Bjorn)

Signed-off-by: Daniel Vetter <[email protected]>
Cc: Stephen Rothwell <[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]
---
drivers/pci/pci-sysfs.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index fb072f4b3176..0c45b4f7b214 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b)
{
int error;

+ if (!sysfs_initialized)
+ return;
+
b->legacy_io = kcalloc(2, sizeof(struct bin_attribute),
GFP_ATOMIC);
if (!b->legacy_io)
@@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
static int __init pci_sysfs_init(void)
{
struct pci_dev *pdev = NULL;
+ struct pci_bus *pbus = NULL;
int retval;

sysfs_initialized = 1;
@@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void)
}
}

+ while ((pbus = pci_find_next_bus(pbus)))
+ pci_create_legacy_files(pbus);
+
return 0;
}
late_initcall(pci_sysfs_init);
--
2.30.0

2021-02-10 17:46:35

by Daniel Vetter

Subject: Re: [PATCH] PCI: Also set up legacy files only after sysfs init

Hi Bjorn,

Can you ack this for merging through my topic branch with the other
follow_pfn/iomem revoke fixes for 5.12?

If not, what's the plan for getting this (or equivalent functionality)
in for 5.13? I have more of these follow_pfn/iomem revoke patches on
top, so I'd like to get the first cut merged sooner than later if
possible. And the other prep work has been in -next since -rc1.

Thanks, Daniel

On Fri, Feb 5, 2021 at 2:36 PM Daniel Vetter <[email protected]> wrote:
>
> We are already doing this for all the regular sysfs files on PCI
> devices, but not yet on the legacy io files on the PCI buses. Thus far
> no problem, but in the next patch I want to wire up iomem revoke
> support. That needs the vfs up and running already to make sure that
> iomem_get_mapping() works.
>
> Wire it up exactly like the existing code in
> pci_create_sysfs_dev_files(). Note that pci_remove_legacy_files()
> doesn't need a check since the one for pci_bus->legacy_io is
> sufficient.
>
> An alternative solution would be to implement a callback in sysfs to
> set up the address space from iomem_get_mapping() when userspace calls
> mmap(). This also works, but Greg didn't really like that just to work
> around an ordering issue when the kernel loads initially.
>
> v2: Improve commit message (Bjorn)
>
> Signed-off-by: Daniel Vetter <[email protected]>
> Cc: Stephen Rothwell <[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]
> ---
> drivers/pci/pci-sysfs.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index fb072f4b3176..0c45b4f7b214 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b)
> {
> int error;
>
> + if (!sysfs_initialized)
> + return;
> +
> b->legacy_io = kcalloc(2, sizeof(struct bin_attribute),
> GFP_ATOMIC);
> if (!b->legacy_io)
> @@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
> static int __init pci_sysfs_init(void)
> {
> struct pci_dev *pdev = NULL;
> + struct pci_bus *pbus = NULL;
> int retval;
>
> sysfs_initialized = 1;
> @@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void)
> }
> }
>
> + while ((pbus = pci_find_next_bus(pbus)))
> + pci_create_legacy_files(pbus);
> +
> return 0;
> }
> late_initcall(pci_sysfs_init);
> --
> 2.30.0
>


--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

2021-02-10 21:42:46

by Bjorn Helgaas

Subject: Re: [PATCH] PCI: Also set up legacy files only after sysfs init

On Fri, Feb 05, 2021 at 02:36:32PM +0100, Daniel Vetter wrote:
> We are already doing this for all the regular sysfs files on PCI
> devices, but not yet on the legacy io files on the PCI buses. Thus far
> no problem, but in the next patch I want to wire up iomem revoke
> support. That needs the vfs up and running already to make sure that
> iomem_get_mapping() works.
>
> Wire it up exactly like the existing code in
> pci_create_sysfs_dev_files(). Note that pci_remove_legacy_files()
> doesn't need a check since the one for pci_bus->legacy_io is
> sufficient.
>
> An alternative solution would be to implement a callback in sysfs to
> set up the address space from iomem_get_mapping() when userspace calls
> mmap(). This also works, but Greg didn't really like that just to work
> around an ordering issue when the kernel loads initially.
>
> v2: Improve commit message (Bjorn)
>
> Signed-off-by: Daniel Vetter <[email protected]>

Acked-by: Bjorn Helgaas <[email protected]>

I wish we weren't extending a known-racy mechanism to do this, but at
least we're not *adding* a brand new race.

> Cc: Stephen Rothwell <[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]
> ---
> drivers/pci/pci-sysfs.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index fb072f4b3176..0c45b4f7b214 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b)
> {
> int error;
>
> + if (!sysfs_initialized)
> + return;
> +
> b->legacy_io = kcalloc(2, sizeof(struct bin_attribute),
> GFP_ATOMIC);
> if (!b->legacy_io)
> @@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
> static int __init pci_sysfs_init(void)
> {
> struct pci_dev *pdev = NULL;
> + struct pci_bus *pbus = NULL;
> int retval;
>
> sysfs_initialized = 1;
> @@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void)
> }
> }
>
> + while ((pbus = pci_find_next_bus(pbus)))
> + pci_create_legacy_files(pbus);
> +
> return 0;
> }
> late_initcall(pci_sysfs_init);
> --
> 2.30.0
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

2021-02-11 15:26:51

by Daniel Vetter

Subject: Re: [PATCH] PCI: Also set up legacy files only after sysfs init

On Wed, Feb 10, 2021 at 10:40 PM Bjorn Helgaas <[email protected]> wrote:
>
> On Fri, Feb 05, 2021 at 02:36:32PM +0100, Daniel Vetter wrote:
> > We are already doing this for all the regular sysfs files on PCI
> > devices, but not yet on the legacy io files on the PCI buses. Thus far
> > no problem, but in the next patch I want to wire up iomem revoke
> > support. That needs the vfs up and running already to make sure that
> > iomem_get_mapping() works.
> >
> > Wire it up exactly like the existing code in
> > pci_create_sysfs_dev_files(). Note that pci_remove_legacy_files()
> > doesn't need a check since the one for pci_bus->legacy_io is
> > sufficient.
> >
> > An alternative solution would be to implement a callback in sysfs to
> > set up the address space from iomem_get_mapping() when userspace calls
> > mmap(). This also works, but Greg didn't really like that just to work
> > around an ordering issue when the kernel loads initially.
> >
> > v2: Improve commit message (Bjorn)
> >
> > Signed-off-by: Daniel Vetter <[email protected]>
>
> Acked-by: Bjorn Helgaas <[email protected]>
>
> I wish we weren't extending a known-racy mechanism to do this, but at
> least we're not *adding* a brand new race.

Yeah it's not great. Thanks for looking at both again, I'll fix up the
typos on the 2nd one and merge them both.

Cheers, Daniel

>
> > Cc: Stephen Rothwell <[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]
> > ---
> > drivers/pci/pci-sysfs.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index fb072f4b3176..0c45b4f7b214 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -927,6 +927,9 @@ void pci_create_legacy_files(struct pci_bus *b)
> > {
> > int error;
> >
> > + if (!sysfs_initialized)
> > + return;
> > +
> > b->legacy_io = kcalloc(2, sizeof(struct bin_attribute),
> > GFP_ATOMIC);
> > if (!b->legacy_io)
> > @@ -1448,6 +1451,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
> > static int __init pci_sysfs_init(void)
> > {
> > struct pci_dev *pdev = NULL;
> > + struct pci_bus *pbus = NULL;
> > int retval;
> >
> > sysfs_initialized = 1;
> > @@ -1459,6 +1463,9 @@ static int __init pci_sysfs_init(void)
> > }
> > }
> >
> > + while ((pbus = pci_find_next_bus(pbus)))
> > + pci_create_legacy_files(pbus);
> > +
> > return 0;
> > }
> > late_initcall(pci_sysfs_init);
> > --
> > 2.30.0
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > [email protected]
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel



--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch