[RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Ard Biesheuvel]

Linux on arm64 is now in the same boat as x86, where supporting laptops
that were built to run Windows and never tested beyond what is required
for the Windows Logo certification need workarounds for all kinds of
bizarre behaviors.

On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
stub, because the firmware will crash while trying to access memory via
the virtual addresses being installed, which is explicitly unsupported
by the EFI spec.

However, not calling SetVirtualAddressMap() results in other problems:
on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
Windows-on-ARM laptops, it causes ResetSystem() to crash.

So let's try to work around this while not making too much of a mess.

First of all, install a 1:1 mapping instead of avoiding SetVaMap()
altogether - from the EFI spec pov, this should amount to the same
thing.

Then, given that we already use a SMBIOS based hack for Altra to force
the use of SetVirtualAddressMap(), let's check for Surface systems in
the same way.

Please test, and please report the SMBIOS type 1 family field for which
this workaround is needed.

Also, note that these changes will not make a difference if the
EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.

Nathan, I would appreciate it if you could give this a spin on your
Altra box (only patch #1 should make a difference), and for good
measure, double check that hwclock still works as it should.

Cc: Johan Hovold <johan+linaro@kernel.org>
Cc: Maximilian Luz <luzmaximilian@gmail.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Steev Klimaszewski <steev@kali.org>
Cc: Shawn Guo <shawn.guo@linaro.org>

Ard Biesheuvel (2):
  arm64: efi: Prefer a flat virtual mapping of the runtime services
  arm64: efi: Force use of SetVirtualAddressMap() on MS Surface

 arch/arm64/include/asm/efi.h            | 2 ++
 drivers/firmware/efi/libstub/arm64.c    | 3 ++-
 drivers/firmware/efi/libstub/efi-stub.c | 6 +++++-
 3 files changed, 9 insertions(+), 2 deletions(-)

-- 
2.39.0


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[RFT PATCH 1/2] arm64: efi: Prefer a flat virtual mapping of the runtime services

[Ard Biesheuvel]

With some systems, we cannot omit the boot time call to
SetVirtualAddressMap() even if the kernel VA space is sufficiently
large, because some buggy EFI implementations exist that misbehave if
SetVirtualAddressMap() is never called.

However, this does not mean we must reshuffle the EFI memory map: we can
simply invoke SetVirtualAddressMap() with a memory map that places each
EFI runtime region at the same virtual address that it takes up in the
physical address map.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/efi.h            | 2 ++
 drivers/firmware/efi/libstub/efi-stub.c | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index de4ff90785b2c96a..98c4dc4da5a90e8c 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -114,6 +114,8 @@ static inline unsigned long efi_get_kimg_min_align(void)
 #define EFI_ALLOC_ALIGN		SZ_64K
 #define EFI_ALLOC_LIMIT		((1UL << 48) - 1)
 
+#define EFI_USE_FLAT_VA_MAPPING	(VA_BITS_MIN >= 48)
+
 /*
  * On ARM systems, virtually remapped UEFI runtime services are set up in two
  * distinct stages:
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index 2955c1ac6a36ee00..40869320d601492a 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -44,8 +44,12 @@
 #define EFI_RT_VIRTUAL_OFFSET	0
 #endif
 
+#ifndef EFI_USE_FLAT_VA_MAPPING
+#define EFI_USE_FLAT_VA_MAPPING	(EFI_RT_VIRTUAL_OFFSET != 0)
+#endif
+
 static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
-static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
+static bool flat_va_mapping = EFI_USE_FLAT_VA_MAPPING;
 
 struct screen_info * __weak alloc_screen_info(void)
 {
-- 
2.39.0


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[RFT PATCH 2/2] arm64: efi: Force use of SetVirtualAddressMap() on MS Surface

[Ard Biesheuvel]

Qualcomm Snapdragon based Surface machines crash in the ResetSystem()
EFI runtime service if SetVirtualAddressMap() has not been called prior.

Unfortunately, SetVirtualAddressMap() itself crashes at boot time unless
the mapping being installed is a 1:1 mapping, as these firmware
implementations violate the EFI spec by accessing the new mapping before
SetVirtualAddressMap() completes.

Now that we have worked around the latter issue by always using a 1:1
map when the size of the VA space permits it, we can safely call
SetVirtualAddressMap() in such cases.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/firmware/efi/libstub/arm64.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/arm64.c b/drivers/firmware/efi/libstub/arm64.c
index ff2d18c42ee74979..cc3757fc29bdda24 100644
--- a/drivers/firmware/efi/libstub/arm64.c
+++ b/drivers/firmware/efi/libstub/arm64.c
@@ -22,7 +22,8 @@ static bool system_needs_vamap(void)
 	 * Ampere Altra machines crash in SetTime() if SetVirtualAddressMap()
 	 * has not been called prior.
 	 */
-	if (!type1_family || strcmp(type1_family, "Altra"))
+	if (!type1_family ||
+	    (strcmp(type1_family, "Altra") && strcmp(type1_family, "Surface")))
 		return false;
 
 	efi_warn("Working around broken SetVirtualAddressMap()\n");
-- 
2.39.0


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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Ard Biesheuvel]

On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
>
> Linux on arm64 is now in the same boat as x86, where supporting laptops
> that were built to run Windows and never tested beyond what is required
> for the Windows Logo certification need workarounds for all kinds of
> bizarre behaviors.
>
> On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> stub, because the firmware will crash while trying to access memory via
> the virtual addresses being installed, which is explicitly unsupported
> by the EFI spec.
>
> However, not calling SetVirtualAddressMap() results in other problems:
> on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> Windows-on-ARM laptops, it causes ResetSystem() to crash.
>
> So let's try to work around this while not making too much of a mess.
>
> First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> altogether - from the EFI spec pov, this should amount to the same
> thing.
>
> Then, given that we already use a SMBIOS based hack for Altra to force
> the use of SetVirtualAddressMap(), let's check for Surface systems in
> the same way.
>
> Please test, and please report the SMBIOS type 1 family field for which
> this workaround is needed.
>
> Also, note that these changes will not make a difference if the
> EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
>
> Nathan, I would appreciate it if you could give this a spin on your
> Altra box (only patch #1 should make a difference), and for good
> measure, double check that hwclock still works as it should.
>
> Cc: Johan Hovold <johan+linaro@kernel.org>
> Cc: Maximilian Luz <luzmaximilian@gmail.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Steev Klimaszewski <steev@kali.org>
> Cc: Shawn Guo <shawn.guo@linaro.org>
>
> Ard Biesheuvel (2):
>   arm64: efi: Prefer a flat virtual mapping of the runtime services
>   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
>

Bah this does not even work on Yoga C630, so this is not going to help us.

If we want ResetSystem() on these machines, we'll have to retain other
memory ranges and map the in the EFI runtime map. Yuck.

Nathan - still interested in whether patch #1 works on Altra,

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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Nathan Chancellor]

On Tue, Jan 17, 2023 at 04:20:09PM +0100, Ard Biesheuvel wrote:
> On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
> >
> > Linux on arm64 is now in the same boat as x86, where supporting laptops
> > that were built to run Windows and never tested beyond what is required
> > for the Windows Logo certification need workarounds for all kinds of
> > bizarre behaviors.
> >
> > On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> > stub, because the firmware will crash while trying to access memory via
> > the virtual addresses being installed, which is explicitly unsupported
> > by the EFI spec.
> >
> > However, not calling SetVirtualAddressMap() results in other problems:
> > on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> > Windows-on-ARM laptops, it causes ResetSystem() to crash.
> >
> > So let's try to work around this while not making too much of a mess.
> >
> > First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> > altogether - from the EFI spec pov, this should amount to the same
> > thing.
> >
> > Then, given that we already use a SMBIOS based hack for Altra to force
> > the use of SetVirtualAddressMap(), let's check for Surface systems in
> > the same way.
> >
> > Please test, and please report the SMBIOS type 1 family field for which
> > this workaround is needed.
> >
> > Also, note that these changes will not make a difference if the
> > EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
> >
> > Nathan, I would appreciate it if you could give this a spin on your
> > Altra box (only patch #1 should make a difference), and for good
> > measure, double check that hwclock still works as it should.
> >
> > Cc: Johan Hovold <johan+linaro@kernel.org>
> > Cc: Maximilian Luz <luzmaximilian@gmail.com>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Cc: Steev Klimaszewski <steev@kali.org>
> > Cc: Shawn Guo <shawn.guo@linaro.org>
> >
> > Ard Biesheuvel (2):
> >   arm64: efi: Prefer a flat virtual mapping of the runtime services
> >   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
> >
> 
> Bah this does not even work on Yoga C630, so this is not going to help us.
> 
> If we want ResetSystem() on these machines, we'll have to retain other
> memory ranges and map the in the EFI runtime map. Yuck.
> 
> Nathan - still interested in whether patch #1 works on Altra,

I applied patch 1 on top of commit 6e50979a9c87 ("Merge tag
'mm-hotfixes-stable-2023-01-16-15-23' of
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") in Linus' tree
and everything still appears to be okay with hwclock. If there is any
more specific testing that I should do, please let me know. Feel free to
add

    Tested-by: Nathan Chancellor <nathan@kernel.org>

to patch 1 in future revisions, and I am happy to test anything else
that you might need in this series or future ones.

Mainline:

# uname -mr
6.2.0-rc4-00031-g6e50979a9c87 aarch64

# hwclock
2023-01-17 09:04:58.845411-07:00

Patch:

# uname -mr
6.2.0-rc4-00032-g20165e83052e aarch64

# hwclock
2023-01-17 10:25:38.843788-07:00

Cheers,
Nathan

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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Ard Biesheuvel]

On Tue, 17 Jan 2023 at 18:30, Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Tue, Jan 17, 2023 at 04:20:09PM +0100, Ard Biesheuvel wrote:
> > On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
> > >
> > > Linux on arm64 is now in the same boat as x86, where supporting laptops
> > > that were built to run Windows and never tested beyond what is required
> > > for the Windows Logo certification need workarounds for all kinds of
> > > bizarre behaviors.
> > >
> > > On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> > > stub, because the firmware will crash while trying to access memory via
> > > the virtual addresses being installed, which is explicitly unsupported
> > > by the EFI spec.
> > >
> > > However, not calling SetVirtualAddressMap() results in other problems:
> > > on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> > > Windows-on-ARM laptops, it causes ResetSystem() to crash.
> > >
> > > So let's try to work around this while not making too much of a mess.
> > >
> > > First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> > > altogether - from the EFI spec pov, this should amount to the same
> > > thing.
> > >
> > > Then, given that we already use a SMBIOS based hack for Altra to force
> > > the use of SetVirtualAddressMap(), let's check for Surface systems in
> > > the same way.
> > >
> > > Please test, and please report the SMBIOS type 1 family field for which
> > > this workaround is needed.
> > >
> > > Also, note that these changes will not make a difference if the
> > > EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
> > >
> > > Nathan, I would appreciate it if you could give this a spin on your
> > > Altra box (only patch #1 should make a difference), and for good
> > > measure, double check that hwclock still works as it should.
> > >
> > > Cc: Johan Hovold <johan+linaro@kernel.org>
> > > Cc: Maximilian Luz <luzmaximilian@gmail.com>
> > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > Cc: Steev Klimaszewski <steev@kali.org>
> > > Cc: Shawn Guo <shawn.guo@linaro.org>
> > >
> > > Ard Biesheuvel (2):
> > >   arm64: efi: Prefer a flat virtual mapping of the runtime services
> > >   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
> > >
> >
> > Bah this does not even work on Yoga C630, so this is not going to help us.
> >
> > If we want ResetSystem() on these machines, we'll have to retain other
> > memory ranges and map the in the EFI runtime map. Yuck.
> >
> > Nathan - still interested in whether patch #1 works on Altra,
>
> I applied patch 1 on top of commit 6e50979a9c87 ("Merge tag
> 'mm-hotfixes-stable-2023-01-16-15-23' of
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") in Linus' tree
> and everything still appears to be okay with hwclock. If there is any
> more specific testing that I should do, please let me know. Feel free to
> add
>
>     Tested-by: Nathan Chancellor <nathan@kernel.org>
>
> to patch 1 in future revisions, and I am happy to test anything else
> that you might need in this series or future ones.
>
> Mainline:
>
> # uname -mr
> 6.2.0-rc4-00031-g6e50979a9c87 aarch64
>
> # hwclock
> 2023-01-17 09:04:58.845411-07:00
>
> Patch:
>
> # uname -mr
> 6.2.0-rc4-00032-g20165e83052e aarch64
>
> # hwclock
> 2023-01-17 10:25:38.843788-07:00
>

Thanks Nathan,

Forgot to mention, though: it is SetTime() not GetTime() that is
problematic on this platform. Could you please double check whether
setting the RTC using hwclock works too?

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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Nathan Chancellor]

On Wed, Jan 18, 2023 at 08:56:54AM +0100, Ard Biesheuvel wrote:
> On Tue, 17 Jan 2023 at 18:30, Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > On Tue, Jan 17, 2023 at 04:20:09PM +0100, Ard Biesheuvel wrote:
> > > On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
> > > >
> > > > Linux on arm64 is now in the same boat as x86, where supporting laptops
> > > > that were built to run Windows and never tested beyond what is required
> > > > for the Windows Logo certification need workarounds for all kinds of
> > > > bizarre behaviors.
> > > >
> > > > On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> > > > stub, because the firmware will crash while trying to access memory via
> > > > the virtual addresses being installed, which is explicitly unsupported
> > > > by the EFI spec.
> > > >
> > > > However, not calling SetVirtualAddressMap() results in other problems:
> > > > on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> > > > Windows-on-ARM laptops, it causes ResetSystem() to crash.
> > > >
> > > > So let's try to work around this while not making too much of a mess.
> > > >
> > > > First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> > > > altogether - from the EFI spec pov, this should amount to the same
> > > > thing.
> > > >
> > > > Then, given that we already use a SMBIOS based hack for Altra to force
> > > > the use of SetVirtualAddressMap(), let's check for Surface systems in
> > > > the same way.
> > > >
> > > > Please test, and please report the SMBIOS type 1 family field for which
> > > > this workaround is needed.
> > > >
> > > > Also, note that these changes will not make a difference if the
> > > > EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
> > > >
> > > > Nathan, I would appreciate it if you could give this a spin on your
> > > > Altra box (only patch #1 should make a difference), and for good
> > > > measure, double check that hwclock still works as it should.
> > > >
> > > > Cc: Johan Hovold <johan+linaro@kernel.org>
> > > > Cc: Maximilian Luz <luzmaximilian@gmail.com>
> > > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > > Cc: Steev Klimaszewski <steev@kali.org>
> > > > Cc: Shawn Guo <shawn.guo@linaro.org>
> > > >
> > > > Ard Biesheuvel (2):
> > > >   arm64: efi: Prefer a flat virtual mapping of the runtime services
> > > >   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
> > > >
> > >
> > > Bah this does not even work on Yoga C630, so this is not going to help us.
> > >
> > > If we want ResetSystem() on these machines, we'll have to retain other
> > > memory ranges and map the in the EFI runtime map. Yuck.
> > >
> > > Nathan - still interested in whether patch #1 works on Altra,
> >
> > I applied patch 1 on top of commit 6e50979a9c87 ("Merge tag
> > 'mm-hotfixes-stable-2023-01-16-15-23' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") in Linus' tree
> > and everything still appears to be okay with hwclock. If there is any
> > more specific testing that I should do, please let me know. Feel free to
> > add
> >
> >     Tested-by: Nathan Chancellor <nathan@kernel.org>
> >
> > to patch 1 in future revisions, and I am happy to test anything else
> > that you might need in this series or future ones.
> >
> > Mainline:
> >
> > # uname -mr
> > 6.2.0-rc4-00031-g6e50979a9c87 aarch64
> >
> > # hwclock
> > 2023-01-17 09:04:58.845411-07:00
> >
> > Patch:
> >
> > # uname -mr
> > 6.2.0-rc4-00032-g20165e83052e aarch64
> >
> > # hwclock
> > 2023-01-17 10:25:38.843788-07:00
> >
> 
> Thanks Nathan,
> 
> Forgot to mention, though: it is SetTime() not GetTime() that is
> problematic on this platform. Could you please double check whether
> setting the RTC using hwclock works too?

Ah, okay, makes sense! As far as I can tell, that works too.

Mainline:

# uname -mr
6.2.0-rc4-00031-g6e50979a9c87 aarch64

# hwclock --systohc

# echo $status
0

Patch:

# uname -mr
6.2.0-rc4-00032-g20165e83052e aarch64

# hwclock --systohc

# echo $status
0

Cheers,
Nathan

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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Ard Biesheuvel]

On Wed, 18 Jan 2023 at 16:26, Nathan Chancellor <nathan@kernel.org> wrote:
>
> On Wed, Jan 18, 2023 at 08:56:54AM +0100, Ard Biesheuvel wrote:
> > On Tue, 17 Jan 2023 at 18:30, Nathan Chancellor <nathan@kernel.org> wrote:
> > >
> > > On Tue, Jan 17, 2023 at 04:20:09PM +0100, Ard Biesheuvel wrote:
> > > > On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
> > > > >
> > > > > Linux on arm64 is now in the same boat as x86, where supporting laptops
> > > > > that were built to run Windows and never tested beyond what is required
> > > > > for the Windows Logo certification need workarounds for all kinds of
> > > > > bizarre behaviors.
> > > > >
> > > > > On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> > > > > stub, because the firmware will crash while trying to access memory via
> > > > > the virtual addresses being installed, which is explicitly unsupported
> > > > > by the EFI spec.
> > > > >
> > > > > However, not calling SetVirtualAddressMap() results in other problems:
> > > > > on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> > > > > Windows-on-ARM laptops, it causes ResetSystem() to crash.
> > > > >
> > > > > So let's try to work around this while not making too much of a mess.
> > > > >
> > > > > First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> > > > > altogether - from the EFI spec pov, this should amount to the same
> > > > > thing.
> > > > >
> > > > > Then, given that we already use a SMBIOS based hack for Altra to force
> > > > > the use of SetVirtualAddressMap(), let's check for Surface systems in
> > > > > the same way.
> > > > >
> > > > > Please test, and please report the SMBIOS type 1 family field for which
> > > > > this workaround is needed.
> > > > >
> > > > > Also, note that these changes will not make a difference if the
> > > > > EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
> > > > >
> > > > > Nathan, I would appreciate it if you could give this a spin on your
> > > > > Altra box (only patch #1 should make a difference), and for good
> > > > > measure, double check that hwclock still works as it should.
> > > > >
> > > > > Cc: Johan Hovold <johan+linaro@kernel.org>
> > > > > Cc: Maximilian Luz <luzmaximilian@gmail.com>
> > > > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > > > Cc: Steev Klimaszewski <steev@kali.org>
> > > > > Cc: Shawn Guo <shawn.guo@linaro.org>
> > > > >
> > > > > Ard Biesheuvel (2):
> > > > >   arm64: efi: Prefer a flat virtual mapping of the runtime services
> > > > >   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
> > > > >
> > > >
> > > > Bah this does not even work on Yoga C630, so this is not going to help us.
> > > >
> > > > If we want ResetSystem() on these machines, we'll have to retain other
> > > > memory ranges and map the in the EFI runtime map. Yuck.
> > > >
> > > > Nathan - still interested in whether patch #1 works on Altra,
> > >
> > > I applied patch 1 on top of commit 6e50979a9c87 ("Merge tag
> > > 'mm-hotfixes-stable-2023-01-16-15-23' of
> > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") in Linus' tree
> > > and everything still appears to be okay with hwclock. If there is any
> > > more specific testing that I should do, please let me know. Feel free to
> > > add
> > >
> > >     Tested-by: Nathan Chancellor <nathan@kernel.org>
> > >
> > > to patch 1 in future revisions, and I am happy to test anything else
> > > that you might need in this series or future ones.
> > >
> > > Mainline:
> > >
> > > # uname -mr
> > > 6.2.0-rc4-00031-g6e50979a9c87 aarch64
> > >
> > > # hwclock
> > > 2023-01-17 09:04:58.845411-07:00
> > >
> > > Patch:
> > >
> > > # uname -mr
> > > 6.2.0-rc4-00032-g20165e83052e aarch64
> > >
> > > # hwclock
> > > 2023-01-17 10:25:38.843788-07:00
> > >
> >
> > Thanks Nathan,
> >
> > Forgot to mention, though: it is SetTime() not GetTime() that is
> > problematic on this platform. Could you please double check whether
> > setting the RTC using hwclock works too?
>
> Ah, okay, makes sense! As far as I can tell, that works too.
>
> Mainline:
>
> # uname -mr
> 6.2.0-rc4-00031-g6e50979a9c87 aarch64
>
> # hwclock --systohc
>
> # echo $status
> 0
>
> Patch:
>
> # uname -mr
> 6.2.0-rc4-00032-g20165e83052e aarch64
>
> # hwclock --systohc
>
> # echo $status
> 0
>

Thanks again!

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Re: [RFT PATCH 0/2] arm64: efi: Call SetVaMap() with a 1:1 mapping

[Darren Hart]

On Wed, Jan 18, 2023 at 04:33:29PM +0100, Ard Biesheuvel wrote:
> On Wed, 18 Jan 2023 at 16:26, Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > On Wed, Jan 18, 2023 at 08:56:54AM +0100, Ard Biesheuvel wrote:
> > > On Tue, 17 Jan 2023 at 18:30, Nathan Chancellor <nathan@kernel.org> wrote:
> > > >
> > > > On Tue, Jan 17, 2023 at 04:20:09PM +0100, Ard Biesheuvel wrote:
> > > > > On Tue, 17 Jan 2023 at 15:27, Ard Biesheuvel <ardb@kernel.org> wrote:
> > > > > >
> > > > > > Linux on arm64 is now in the same boat as x86, where supporting laptops
> > > > > > that were built to run Windows and never tested beyond what is required
> > > > > > for the Windows Logo certification need workarounds for all kinds of
> > > > > > bizarre behaviors.
> > > > > >
> > > > > > On Snapdragon laptops, we cannot call SetVirtualAddressMap() from the
> > > > > > stub, because the firmware will crash while trying to access memory via
> > > > > > the virtual addresses being installed, which is explicitly unsupported
> > > > > > by the EFI spec.
> > > > > >
> > > > > > However, not calling SetVirtualAddressMap() results in other problems:
> > > > > > on Ampere Altra, it causes SetTime() to crash. On Surface and Flex5g
> > > > > > Windows-on-ARM laptops, it causes ResetSystem() to crash.
> > > > > >
> > > > > > So let's try to work around this while not making too much of a mess.
> > > > > >
> > > > > > First of all, install a 1:1 mapping instead of avoiding SetVaMap()
> > > > > > altogether - from the EFI spec pov, this should amount to the same
> > > > > > thing.
> > > > > >
> > > > > > Then, given that we already use a SMBIOS based hack for Altra to force
> > > > > > the use of SetVirtualAddressMap(), let's check for Surface systems in
> > > > > > the same way.
> > > > > >
> > > > > > Please test, and please report the SMBIOS type 1 family field for which
> > > > > > this workaround is needed.
> > > > > >
> > > > > > Also, note that these changes will not make a difference if the
> > > > > > EFI_RT_PROPERTIES_TABLE lists SetVirtualAddressMap() as not implemented.
> > > > > >
> > > > > > Nathan, I would appreciate it if you could give this a spin on your
> > > > > > Altra box (only patch #1 should make a difference), and for good
> > > > > > measure, double check that hwclock still works as it should.
> > > > > >
> > > > > > Cc: Johan Hovold <johan+linaro@kernel.org>
> > > > > > Cc: Maximilian Luz <luzmaximilian@gmail.com>
> > > > > > Cc: Nathan Chancellor <nathan@kernel.org>
> > > > > > Cc: Steev Klimaszewski <steev@kali.org>
> > > > > > Cc: Shawn Guo <shawn.guo@linaro.org>
> > > > > >
> > > > > > Ard Biesheuvel (2):
> > > > > >   arm64: efi: Prefer a flat virtual mapping of the runtime services
> > > > > >   arm64: efi: Force use of SetVirtualAddressMap() on MS Surface
> > > > > >
> > > > >
> > > > > Bah this does not even work on Yoga C630, so this is not going to help us.
> > > > >
> > > > > If we want ResetSystem() on these machines, we'll have to retain other
> > > > > memory ranges and map the in the EFI runtime map. Yuck.
> > > > >
> > > > > Nathan - still interested in whether patch #1 works on Altra,
> > > >
> > > > I applied patch 1 on top of commit 6e50979a9c87 ("Merge tag
> > > > 'mm-hotfixes-stable-2023-01-16-15-23' of
> > > > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm") in Linus' tree
> > > > and everything still appears to be okay with hwclock. If there is any
> > > > more specific testing that I should do, please let me know. Feel free to
> > > > add
> > > >
> > > >     Tested-by: Nathan Chancellor <nathan@kernel.org>
> > > >
> > > > to patch 1 in future revisions, and I am happy to test anything else
> > > > that you might need in this series or future ones.
> > > >
> > > > Mainline:
> > > >
> > > > # uname -mr
> > > > 6.2.0-rc4-00031-g6e50979a9c87 aarch64
> > > >
> > > > # hwclock
> > > > 2023-01-17 09:04:58.845411-07:00
> > > >
> > > > Patch:
> > > >
> > > > # uname -mr
> > > > 6.2.0-rc4-00032-g20165e83052e aarch64
> > > >
> > > > # hwclock
> > > > 2023-01-17 10:25:38.843788-07:00
> > > >
> > >
> > > Thanks Nathan,
> > >
> > > Forgot to mention, though: it is SetTime() not GetTime() that is
> > > problematic on this platform. Could you please double check whether
> > > setting the RTC using hwclock works too?

The other runtime service that triggers this is SetVariable, which I have been
testing like this. The tests still pass on systems with the affected firmware
with the SMBIOS string mitigation in place and this flat va mapping applied.

#!/bin/sh

function set_timeout() {
	TO=$1

	re='^[0-9]$'
	if ! [[ "$TO" =~ $re ]]; then
		echo "Timeout must be 0-9"
		exit 1
	fi

	efibootmgr -t $TO > /dev/null
	efivar -n 8be4df61-93ca-11d2-aa0d-00e098032b8c-Timeout | grep -q "00000000  0$TO 00"
	if [ $? -ne 0 ]; then
		echo "ERROR: timeout $TO not reflected in efivar"
		exit 1
	fi
	echo "SUCCESS: timeout $TO reflected in efivar"
	return 0
}

set_timeout 4
set_timeout 5
exit 0

Thanks,

Darren

> >
> > Ah, okay, makes sense! As far as I can tell, that works too.
> >
> > Mainline:
> >
> > # uname -mr
> > 6.2.0-rc4-00031-g6e50979a9c87 aarch64
> >
> > # hwclock --systohc
> >
> > # echo $status
> > 0
> >
> > Patch:
> >
> > # uname -mr
> > 6.2.0-rc4-00032-g20165e83052e aarch64
> >
> > # hwclock --systohc
> >
> > # echo $status
> > 0
> >
> 
> Thanks again!

-- 
Darren Hart
Ampere Computing / OS and Kernel

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