The TPM event log is provided to the OS by the firmware, by loading
it into an area in memory and passing the physical address via a node
in the device tree.
Currently, we use __va() to access the memory via the kernel's linear
map: however, it is not guaranteed that the linear map covers this
particular address, as we may be running under HIGHMEM on a 32-bit
architecture, or running firmware that uses a memory type for the
event log that is omitted from the linear map (such as EfiReserved).
So instead, use memremap(), which will reuse the linear mapping if
it is valid, or create another mapping otherwise.
Cc: Peter Huewe <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
---
drivers/char/tpm/eventlog/of.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
index a9ce66d09a75..9178547589a3 100644
--- a/drivers/char/tpm/eventlog/of.c
+++ b/drivers/char/tpm/eventlog/of.c
@@ -11,6 +11,7 @@
*/
#include <linux/slab.h>
+#include <linux/io.h>
#include <linux/of.h>
#include <linux/tpm_eventlog.h>
@@ -25,6 +26,7 @@ int tpm_read_log_of(struct tpm_chip *chip)
struct tpm_bios_log *log;
u32 size;
u64 base;
+ void *p;
log = &chip->log;
if (chip->dev.parent && chip->dev.parent->of_node)
@@ -65,7 +67,11 @@ int tpm_read_log_of(struct tpm_chip *chip)
return -EIO;
}
- log->bios_event_log = kmemdup(__va(base), size, GFP_KERNEL);
+ p = memremap(base, size, MEMREMAP_WB);
+ if (!p)
+ return -ENOMEM;
+ log->bios_event_log = kmemdup(p, size, GFP_KERNEL);
+ memunmap(p);
if (!log->bios_event_log)
return -ENOMEM;
--
2.17.1
On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> The TPM event log is provided to the OS by the firmware, by loading
> it into an area in memory and passing the physical address via a node
> in the device tree.
>
> Currently, we use __va() to access the memory via the kernel's linear
> map: however, it is not guaranteed that the linear map covers this
> particular address, as we may be running under HIGHMEM on a 32-bit
> architecture, or running firmware that uses a memory type for the
> event log that is omitted from the linear map (such as EfiReserved).
Makes perfect sense to the level that I wonder if this should have a
fixes tag and/or needs to be backported to the stable kernels?
> So instead, use memremap(), which will reuse the linear mapping if
> it is valid, or create another mapping otherwise.
>
> Cc: Peter Huewe <[email protected]>
> Cc: Jarkko Sakkinen <[email protected]>
> Cc: Jason Gunthorpe <[email protected]>
> Signed-off-by: Ard Biesheuvel <[email protected]>
> ---
> drivers/char/tpm/eventlog/of.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
> index a9ce66d09a75..9178547589a3 100644
> --- a/drivers/char/tpm/eventlog/of.c
> +++ b/drivers/char/tpm/eventlog/of.c
> @@ -11,6 +11,7 @@
> */
>
> #include <linux/slab.h>
> +#include <linux/io.h>
> #include <linux/of.h>
> #include <linux/tpm_eventlog.h>
>
> @@ -25,6 +26,7 @@ int tpm_read_log_of(struct tpm_chip *chip)
> struct tpm_bios_log *log;
> u32 size;
> u64 base;
> + void *p;
I'd just use 'ptr' for readability sake.
> log = &chip->log;
> if (chip->dev.parent && chip->dev.parent->of_node)
> @@ -65,7 +67,11 @@ int tpm_read_log_of(struct tpm_chip *chip)
> return -EIO;
> }
>
> - log->bios_event_log = kmemdup(__va(base), size, GFP_KERNEL);
> + p = memremap(base, size, MEMREMAP_WB);
> + if (!p)
> + return -ENOMEM;
> + log->bios_event_log = kmemdup(p, size, GFP_KERNEL);
> + memunmap(p);
> if (!log->bios_event_log)
> return -ENOMEM;
>
> --
> 2.17.1
>
This is a really great catch!
I'm a bit late of my PR a bit because of SGX upstreaming madness
(sending v39 soon). If you can answer to my question above, I can do
that nitpick change to patch and get it to my v5.10 PR.
PS. Just so that you know, once I've applied it, it will be available
here:
git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git
I'll include MAINTAINERS update to that PR.
/Jarkko
On Fri, Sep 25, 2020 at 08:56:30AM +0300, Jarkko Sakkinen wrote:
> On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > The TPM event log is provided to the OS by the firmware, by loading
> > it into an area in memory and passing the physical address via a node
> > in the device tree.
> >
> > Currently, we use __va() to access the memory via the kernel's linear
> > map: however, it is not guaranteed that the linear map covers this
> > particular address, as we may be running under HIGHMEM on a 32-bit
> > architecture, or running firmware that uses a memory type for the
> > event log that is omitted from the linear map (such as EfiReserved).
>
> Makes perfect sense to the level that I wonder if this should have a
> fixes tag and/or needs to be backported to the stable kernels?
>
> > So instead, use memremap(), which will reuse the linear mapping if
> > it is valid, or create another mapping otherwise.
> >
> > Cc: Peter Huewe <[email protected]>
> > Cc: Jarkko Sakkinen <[email protected]>
> > Cc: Jason Gunthorpe <[email protected]>
> > Signed-off-by: Ard Biesheuvel <[email protected]>
> > ---
> > drivers/char/tpm/eventlog/of.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
> > index a9ce66d09a75..9178547589a3 100644
> > --- a/drivers/char/tpm/eventlog/of.c
> > +++ b/drivers/char/tpm/eventlog/of.c
> > @@ -11,6 +11,7 @@
> > */
> >
> > #include <linux/slab.h>
> > +#include <linux/io.h>
> > #include <linux/of.h>
> > #include <linux/tpm_eventlog.h>
> >
> > @@ -25,6 +26,7 @@ int tpm_read_log_of(struct tpm_chip *chip)
> > struct tpm_bios_log *log;
> > u32 size;
> > u64 base;
> > + void *p;
>
> I'd just use 'ptr' for readability sake.
>
> > log = &chip->log;
> > if (chip->dev.parent && chip->dev.parent->of_node)
> > @@ -65,7 +67,11 @@ int tpm_read_log_of(struct tpm_chip *chip)
> > return -EIO;
> > }
> >
> > - log->bios_event_log = kmemdup(__va(base), size, GFP_KERNEL);
> > + p = memremap(base, size, MEMREMAP_WB);
> > + if (!p)
> > + return -ENOMEM;
> > + log->bios_event_log = kmemdup(p, size, GFP_KERNEL);
> > + memunmap(p);
> > if (!log->bios_event_log)
> > return -ENOMEM;
> >
> > --
> > 2.17.1
> >
>
> This is a really great catch!
>
> I'm a bit late of my PR a bit because of SGX upstreaming madness
> (sending v39 soon). If you can answer to my question above, I can do
> that nitpick change to patch and get it to my v5.10 PR.
>
> PS. Just so that you know, once I've applied it, it will be available
> here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git
>
> I'll include MAINTAINERS update to that PR.
Forgot this:
Reviewed-by: Jarkko Sakkinen <[email protected]>
/Jarkko
On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
<[email protected]> wrote:
>
> On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > The TPM event log is provided to the OS by the firmware, by loading
> > it into an area in memory and passing the physical address via a node
> > in the device tree.
> >
> > Currently, we use __va() to access the memory via the kernel's linear
> > map: however, it is not guaranteed that the linear map covers this
> > particular address, as we may be running under HIGHMEM on a 32-bit
> > architecture, or running firmware that uses a memory type for the
> > event log that is omitted from the linear map (such as EfiReserved).
>
> Makes perfect sense to the level that I wonder if this should have a
> fixes tag and/or needs to be backported to the stable kernels?
>
AIUI, the code was written specifically for ppc64, which is a
non-highmem, non-EFI architecture. However, when we start reusing this
driver for ARM, this issue could pop up.
The code itself has been refactored a couple of times, so I think it
will require different versions of the patch for different generations
of stable kernels.
So perhaps just add Cc: <[email protected]>, and wait and see how
far back it applies cleanly?
> > So instead, use memremap(), which will reuse the linear mapping if
> > it is valid, or create another mapping otherwise.
> >
> > Cc: Peter Huewe <[email protected]>
> > Cc: Jarkko Sakkinen <[email protected]>
> > Cc: Jason Gunthorpe <[email protected]>
> > Signed-off-by: Ard Biesheuvel <[email protected]>
> > ---
> > drivers/char/tpm/eventlog/of.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
> > index a9ce66d09a75..9178547589a3 100644
> > --- a/drivers/char/tpm/eventlog/of.c
> > +++ b/drivers/char/tpm/eventlog/of.c
> > @@ -11,6 +11,7 @@
> > */
> >
> > #include <linux/slab.h>
> > +#include <linux/io.h>
> > #include <linux/of.h>
> > #include <linux/tpm_eventlog.h>
> >
> > @@ -25,6 +26,7 @@ int tpm_read_log_of(struct tpm_chip *chip)
> > struct tpm_bios_log *log;
> > u32 size;
> > u64 base;
> > + void *p;
>
> I'd just use 'ptr' for readability sake.
>
If you prefer
> > log = &chip->log;
> > if (chip->dev.parent && chip->dev.parent->of_node)
> > @@ -65,7 +67,11 @@ int tpm_read_log_of(struct tpm_chip *chip)
> > return -EIO;
> > }
> >
> > - log->bios_event_log = kmemdup(__va(base), size, GFP_KERNEL);
> > + p = memremap(base, size, MEMREMAP_WB);
> > + if (!p)
> > + return -ENOMEM;
> > + log->bios_event_log = kmemdup(p, size, GFP_KERNEL);
> > + memunmap(p);
> > if (!log->bios_event_log)
> > return -ENOMEM;
> >
> > --
> > 2.17.1
> >
>
> This is a really great catch!
>
> I'm a bit late of my PR a bit because of SGX upstreaming madness
> (sending v39 soon). If you can answer to my question above, I can do
> that nitpick change to patch and get it to my v5.10 PR.
>
Yes, please.
> PS. Just so that you know, once I've applied it, it will be available
> here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git
>
> I'll include MAINTAINERS update to that PR.
>
> /Jarkko
On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
> On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
> <[email protected]> wrote:
> >
> > On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > > The TPM event log is provided to the OS by the firmware, by loading
> > > it into an area in memory and passing the physical address via a node
> > > in the device tree.
> > >
> > > Currently, we use __va() to access the memory via the kernel's linear
> > > map: however, it is not guaranteed that the linear map covers this
> > > particular address, as we may be running under HIGHMEM on a 32-bit
> > > architecture, or running firmware that uses a memory type for the
> > > event log that is omitted from the linear map (such as EfiReserved).
> >
> > Makes perfect sense to the level that I wonder if this should have a
> > fixes tag and/or needs to be backported to the stable kernels?
> >
>
> AIUI, the code was written specifically for ppc64, which is a
> non-highmem, non-EFI architecture. However, when we start reusing this
> driver for ARM, this issue could pop up.
>
> The code itself has been refactored a couple of times, so I think it
> will require different versions of the patch for different generations
> of stable kernels.
>
> So perhaps just add Cc: <[email protected]>, and wait and see how
> far back it applies cleanly?
Yeah, I think I'll cc it with some note before the diffstat.
I'm thinking to cap it to only 5.x kernels (at least first) unless it is
dead easy to backport below that.
> > This is a really great catch!
> >
> > I'm a bit late of my PR a bit because of SGX upstreaming madness
> > (sending v39 soon). If you can answer to my question above, I can do
> > that nitpick change to patch and get it to my v5.10 PR.
> >
>
> Yes, please.
Great, will do, thanks again for fixing this issue!
/Jarkko
On Fri, Sep 25, 2020 at 01:29:20PM +0300, Jarkko Sakkinen wrote:
> On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
> > On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
> > <[email protected]> wrote:
> > >
> > > On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > > > The TPM event log is provided to the OS by the firmware, by loading
> > > > it into an area in memory and passing the physical address via a node
> > > > in the device tree.
> > > >
> > > > Currently, we use __va() to access the memory via the kernel's linear
> > > > map: however, it is not guaranteed that the linear map covers this
> > > > particular address, as we may be running under HIGHMEM on a 32-bit
> > > > architecture, or running firmware that uses a memory type for the
> > > > event log that is omitted from the linear map (such as EfiReserved).
> > >
> > > Makes perfect sense to the level that I wonder if this should have a
> > > fixes tag and/or needs to be backported to the stable kernels?
> > >
> >
> > AIUI, the code was written specifically for ppc64, which is a
> > non-highmem, non-EFI architecture. However, when we start reusing this
> > driver for ARM, this issue could pop up.
> >
> > The code itself has been refactored a couple of times, so I think it
> > will require different versions of the patch for different generations
> > of stable kernels.
> >
> > So perhaps just add Cc: <[email protected]>, and wait and see how
> > far back it applies cleanly?
>
> Yeah, I think I'll cc it with some note before the diffstat.
>
> I'm thinking to cap it to only 5.x kernels (at least first) unless it is
> dead easy to backport below that.
I have this vauge recollection of pointing at this before and being
told that it had to be __va for some PPC reason?
Do check with the PPC people first, I see none on the CC list.
Jason
On Fri, Sep 25, 2020 at 09:00:18AM -0300, Jason Gunthorpe wrote:
> On Fri, Sep 25, 2020 at 01:29:20PM +0300, Jarkko Sakkinen wrote:
> > On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
> > > On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
> > > <[email protected]> wrote:
> > > >
> > > > On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > > > > The TPM event log is provided to the OS by the firmware, by loading
> > > > > it into an area in memory and passing the physical address via a node
> > > > > in the device tree.
> > > > >
> > > > > Currently, we use __va() to access the memory via the kernel's linear
> > > > > map: however, it is not guaranteed that the linear map covers this
> > > > > particular address, as we may be running under HIGHMEM on a 32-bit
> > > > > architecture, or running firmware that uses a memory type for the
> > > > > event log that is omitted from the linear map (such as EfiReserved).
> > > >
> > > > Makes perfect sense to the level that I wonder if this should have a
> > > > fixes tag and/or needs to be backported to the stable kernels?
> > > >
> > >
> > > AIUI, the code was written specifically for ppc64, which is a
> > > non-highmem, non-EFI architecture. However, when we start reusing this
> > > driver for ARM, this issue could pop up.
> > >
> > > The code itself has been refactored a couple of times, so I think it
> > > will require different versions of the patch for different generations
> > > of stable kernels.
> > >
> > > So perhaps just add Cc: <[email protected]>, and wait and see how
> > > far back it applies cleanly?
> >
> > Yeah, I think I'll cc it with some note before the diffstat.
> >
> > I'm thinking to cap it to only 5.x kernels (at least first) unless it is
> > dead easy to backport below that.
>
> I have this vauge recollection of pointing at this before and being
> told that it had to be __va for some PPC reason?
>
> Do check with the PPC people first, I see none on the CC list.
>
> Jason
Thanks, added arch/powerpc maintainers.
/Jarkko
Le 28/09/2020 à 01:44, Jarkko Sakkinen a écrit :
> On Fri, Sep 25, 2020 at 09:00:18AM -0300, Jason Gunthorpe wrote:
>> On Fri, Sep 25, 2020 at 01:29:20PM +0300, Jarkko Sakkinen wrote:
>>> On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
>>>> On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
>>>> <[email protected]> wrote:
>>>>>
>>>>> On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
>>>>>> The TPM event log is provided to the OS by the firmware, by loading
>>>>>> it into an area in memory and passing the physical address via a node
>>>>>> in the device tree.
>>>>>>
>>>>>> Currently, we use __va() to access the memory via the kernel's linear
>>>>>> map: however, it is not guaranteed that the linear map covers this
>>>>>> particular address, as we may be running under HIGHMEM on a 32-bit
>>>>>> architecture, or running firmware that uses a memory type for the
>>>>>> event log that is omitted from the linear map (such as EfiReserved).
>>>>>
>>>>> Makes perfect sense to the level that I wonder if this should have a
>>>>> fixes tag and/or needs to be backported to the stable kernels?
>>>>>
>>>>
>>>> AIUI, the code was written specifically for ppc64, which is a
>>>> non-highmem, non-EFI architecture. However, when we start reusing this
>>>> driver for ARM, this issue could pop up.
>>>>
>>>> The code itself has been refactored a couple of times, so I think it
>>>> will require different versions of the patch for different generations
>>>> of stable kernels.
>>>>
>>>> So perhaps just add Cc: <[email protected]>, and wait and see how
>>>> far back it applies cleanly?
>>>
>>> Yeah, I think I'll cc it with some note before the diffstat.
>>>
>>> I'm thinking to cap it to only 5.x kernels (at least first) unless it is
>>> dead easy to backport below that.
>>
>> I have this vauge recollection of pointing at this before and being
>> told that it had to be __va for some PPC reason?
>>
>> Do check with the PPC people first, I see none on the CC list.
>>
>> Jason
>
> Thanks, added arch/powerpc maintainers.
>
As far as I can see, memremap() won't work on PPC32 at least:
IIUC, memremap() calls arch_memremap_wb()
arch_memremap_wb() calls ioremap_cache()
In case of failure, then ioremap_wt() and ioremap_wc() are tried.
All ioremap calls end up in __ioremap_caller() which will return NULL in case you try to ioremap RAM.
So the statement "So instead, use memremap(), which will reuse the linear mapping if
it is valid, or create another mapping otherwise." seems to be wrong, at least for PPC32.
Even for PPC64 which doesn't seem to have the RAM check, I can't see that it will "reuse the linear
mapping".
Christophe
On Mon, 28 Sep 2020 at 07:56, Christophe Leroy
<[email protected]> wrote:
>
>
>
> Le 28/09/2020 à 01:44, Jarkko Sakkinen a écrit :
> > On Fri, Sep 25, 2020 at 09:00:18AM -0300, Jason Gunthorpe wrote:
> >> On Fri, Sep 25, 2020 at 01:29:20PM +0300, Jarkko Sakkinen wrote:
> >>> On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
> >>>> On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
> >>>> <[email protected]> wrote:
> >>>>>
> >>>>> On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> >>>>>> The TPM event log is provided to the OS by the firmware, by loading
> >>>>>> it into an area in memory and passing the physical address via a node
> >>>>>> in the device tree.
> >>>>>>
> >>>>>> Currently, we use __va() to access the memory via the kernel's linear
> >>>>>> map: however, it is not guaranteed that the linear map covers this
> >>>>>> particular address, as we may be running under HIGHMEM on a 32-bit
> >>>>>> architecture, or running firmware that uses a memory type for the
> >>>>>> event log that is omitted from the linear map (such as EfiReserved).
> >>>>>
> >>>>> Makes perfect sense to the level that I wonder if this should have a
> >>>>> fixes tag and/or needs to be backported to the stable kernels?
> >>>>>
> >>>>
> >>>> AIUI, the code was written specifically for ppc64, which is a
> >>>> non-highmem, non-EFI architecture. However, when we start reusing this
> >>>> driver for ARM, this issue could pop up.
> >>>>
> >>>> The code itself has been refactored a couple of times, so I think it
> >>>> will require different versions of the patch for different generations
> >>>> of stable kernels.
> >>>>
> >>>> So perhaps just add Cc: <[email protected]>, and wait and see how
> >>>> far back it applies cleanly?
> >>>
> >>> Yeah, I think I'll cc it with some note before the diffstat.
> >>>
> >>> I'm thinking to cap it to only 5.x kernels (at least first) unless it is
> >>> dead easy to backport below that.
> >>
> >> I have this vauge recollection of pointing at this before and being
> >> told that it had to be __va for some PPC reason?
> >>
> >> Do check with the PPC people first, I see none on the CC list.
> >>
> >> Jason
> >
> > Thanks, added arch/powerpc maintainers.
> >
>
> As far as I can see, memremap() won't work on PPC32 at least:
>
> IIUC, memremap() calls arch_memremap_wb()
> arch_memremap_wb() calls ioremap_cache()
> In case of failure, then ioremap_wt() and ioremap_wc() are tried.
>
> All ioremap calls end up in __ioremap_caller() which will return NULL in case you try to ioremap RAM.
>
> So the statement "So instead, use memremap(), which will reuse the linear mapping if
> it is valid, or create another mapping otherwise." seems to be wrong, at least for PPC32.
>
> Even for PPC64 which doesn't seem to have the RAM check, I can't see that it will "reuse the linear
> mapping".
>
It is there, please look again. Before any of the above happens,
memremap() will call try_ram_remap() for regions that are covered by a
IORESOURCE_SYSTEM_RAM, and map it using __va() if its PFN is valid and
it is not highmem.
So as far as I can tell, this change has no effect on PPC at all
unless its RAM is not described as IORESOURCE_SYSTEM_RAM.
On Mon, Sep 28, 2020 at 08:20:18AM +0200, Ard Biesheuvel wrote:
> On Mon, 28 Sep 2020 at 07:56, Christophe Leroy
> <[email protected]> wrote:
> >
> >
> >
> > Le 28/09/2020 ? 01:44, Jarkko Sakkinen a ?crit :
> > > On Fri, Sep 25, 2020 at 09:00:18AM -0300, Jason Gunthorpe wrote:
> > >> On Fri, Sep 25, 2020 at 01:29:20PM +0300, Jarkko Sakkinen wrote:
> > >>> On Fri, Sep 25, 2020 at 09:00:56AM +0200, Ard Biesheuvel wrote:
> > >>>> On Fri, 25 Sep 2020 at 07:56, Jarkko Sakkinen
> > >>>> <[email protected]> wrote:
> > >>>>>
> > >>>>> On Tue, Sep 22, 2020 at 11:41:28AM +0200, Ard Biesheuvel wrote:
> > >>>>>> The TPM event log is provided to the OS by the firmware, by loading
> > >>>>>> it into an area in memory and passing the physical address via a node
> > >>>>>> in the device tree.
> > >>>>>>
> > >>>>>> Currently, we use __va() to access the memory via the kernel's linear
> > >>>>>> map: however, it is not guaranteed that the linear map covers this
> > >>>>>> particular address, as we may be running under HIGHMEM on a 32-bit
> > >>>>>> architecture, or running firmware that uses a memory type for the
> > >>>>>> event log that is omitted from the linear map (such as EfiReserved).
> > >>>>>
> > >>>>> Makes perfect sense to the level that I wonder if this should have a
> > >>>>> fixes tag and/or needs to be backported to the stable kernels?
> > >>>>>
> > >>>>
> > >>>> AIUI, the code was written specifically for ppc64, which is a
> > >>>> non-highmem, non-EFI architecture. However, when we start reusing this
> > >>>> driver for ARM, this issue could pop up.
> > >>>>
> > >>>> The code itself has been refactored a couple of times, so I think it
> > >>>> will require different versions of the patch for different generations
> > >>>> of stable kernels.
> > >>>>
> > >>>> So perhaps just add Cc: <[email protected]>, and wait and see how
> > >>>> far back it applies cleanly?
> > >>>
> > >>> Yeah, I think I'll cc it with some note before the diffstat.
> > >>>
> > >>> I'm thinking to cap it to only 5.x kernels (at least first) unless it is
> > >>> dead easy to backport below that.
> > >>
> > >> I have this vauge recollection of pointing at this before and being
> > >> told that it had to be __va for some PPC reason?
> > >>
> > >> Do check with the PPC people first, I see none on the CC list.
> > >>
> > >> Jason
> > >
> > > Thanks, added arch/powerpc maintainers.
> > >
> >
> > As far as I can see, memremap() won't work on PPC32 at least:
> >
> > IIUC, memremap() calls arch_memremap_wb()
> > arch_memremap_wb() calls ioremap_cache()
> > In case of failure, then ioremap_wt() and ioremap_wc() are tried.
> >
> > All ioremap calls end up in __ioremap_caller() which will return NULL in case you try to ioremap RAM.
> >
> > So the statement "So instead, use memremap(), which will reuse the linear mapping if
> > it is valid, or create another mapping otherwise." seems to be wrong, at least for PPC32.
> >
> > Even for PPC64 which doesn't seem to have the RAM check, I can't see that it will "reuse the linear
> > mapping".
> >
>
> It is there, please look again. Before any of the above happens,
> memremap() will call try_ram_remap() for regions that are covered by a
> IORESOURCE_SYSTEM_RAM, and map it using __va() if its PFN is valid and
> it is not highmem.
>
> So as far as I can tell, this change has no effect on PPC at all
> unless its RAM is not described as IORESOURCE_SYSTEM_RAM.
Any chance for someone to test this on PPC32?
/Jarkko