[PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Ard Biesheuvel]

Hi Matt,

Could we queue this as a fix for v4.6 with a cc:stable for v4.5, please?
(assuming no objections from any of the cc'ees)

Thanks,
Ard.

----------8<--------------
Commit 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as
MEMBLOCK_NOMAP") updated the mapping logic of both the RuntimeServices
regions as well as the kernel's copy of the UEFI memory map to set the
MEMBLOCK_NOMAP flag, which causes these regions to be omitted from the
kernel direct mapping, and from being covered by a struct page.
For the RuntimeServices regions, this is an obvious win, since the contents
of these regions have significance to the firmware executable code itself,
and are mapped in the EFI page tables using attributes that are described in
the UEFI memory map, and which may differ from the attributes we use for
mapping system RAM. It also prevents the contents from being modified
inadvertently, since the EFI page tables are only live during runtime
service invocations.

None of these concerns apply to the allocation that covers the UEFI memory
map, since it is entirely owned by the kernel. Setting the MEMBLOCK_NOMAP on
the region did allow us to use ioremap_cache() to map it both on arm64 and
on ARM, since the latter does not allow ioremap_cache() to be used on
regions that are covered by a struct page.

The ioremap_cache() on ARM restriction will be lifted in the v4.7 timeframe,
but in the mean time, it has been reported that commit 4dffbfc48d65 causes
a regression on 64k granule kernels. This is due to the fact that, given
the 64 KB page size, the region that we end up removing from the kernel
direct mapping is rounded up to 64 KB, and this 64 KB page frame may be
shared with the initrd when booting via GRUB (which does not align its
EFI_LOADER_DATA allocations to 64 KB like the stub does). This will crash
the kernel as soon as it tries to access the initrd.

Since the issue is specific to arm64, revert back to memblock_reserve()'ing
the UEFI memory map when running on arm64. This is a temporary fix for v4.5
and v4.6, and will be superseded in the v4.7 timeframe when we will be able
to move back to memblock_reserve() unconditionally.

Fixes: 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
Reported-by: Mark Salter <msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/firmware/efi/arm-init.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index aa1f743152a2..8714f8c271ba 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -203,7 +203,19 @@ void __init efi_init(void)
 
 	reserve_regions();
 	early_memunmap(memmap.map, params.mmap_size);
-	memblock_mark_nomap(params.mmap & PAGE_MASK,
-			    PAGE_ALIGN(params.mmap_size +
-				       (params.mmap & ~PAGE_MASK)));
+
+	if (IS_ENABLED(CONFIG_ARM)) {
+		/*
+		 * ARM currently does not allow ioremap_cache() to be called on
+		 * memory regions that are covered by struct page. So remove the
+		 * UEFI memory map from the linear mapping.
+		 */
+		memblock_mark_nomap(params.mmap & PAGE_MASK,
+				    PAGE_ALIGN(params.mmap_size +
+					       (params.mmap & ~PAGE_MASK)));
+	} else {
+		memblock_reserve(params.mmap & PAGE_MASK,
+				 PAGE_ALIGN(params.mmap_size +
+					    (params.mmap & ~PAGE_MASK)));
+	}
 }
-- 
2.5.0

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Will Deacon]

On Wed, Mar 30, 2016 at 09:46:23AM +0200, Ard Biesheuvel wrote:
> Hi Matt,
> 
> Could we queue this as a fix for v4.6 with a cc:stable for v4.5, please?
> (assuming no objections from any of the cc'ees)

FWIW:

Acked-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>

Yes, this is a temporary hack, but it's small, fixes a real issue and
you're already working on a proper solution anyway.

Will

> ----------8<--------------
> Commit 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as
> MEMBLOCK_NOMAP") updated the mapping logic of both the RuntimeServices
> regions as well as the kernel's copy of the UEFI memory map to set the
> MEMBLOCK_NOMAP flag, which causes these regions to be omitted from the
> kernel direct mapping, and from being covered by a struct page.
> For the RuntimeServices regions, this is an obvious win, since the contents
> of these regions have significance to the firmware executable code itself,
> and are mapped in the EFI page tables using attributes that are described in
> the UEFI memory map, and which may differ from the attributes we use for
> mapping system RAM. It also prevents the contents from being modified
> inadvertently, since the EFI page tables are only live during runtime
> service invocations.
> 
> None of these concerns apply to the allocation that covers the UEFI memory
> map, since it is entirely owned by the kernel. Setting the MEMBLOCK_NOMAP on
> the region did allow us to use ioremap_cache() to map it both on arm64 and
> on ARM, since the latter does not allow ioremap_cache() to be used on
> regions that are covered by a struct page.
> 
> The ioremap_cache() on ARM restriction will be lifted in the v4.7 timeframe,
> but in the mean time, it has been reported that commit 4dffbfc48d65 causes
> a regression on 64k granule kernels. This is due to the fact that, given
> the 64 KB page size, the region that we end up removing from the kernel
> direct mapping is rounded up to 64 KB, and this 64 KB page frame may be
> shared with the initrd when booting via GRUB (which does not align its
> EFI_LOADER_DATA allocations to 64 KB like the stub does). This will crash
> the kernel as soon as it tries to access the initrd.
> 
> Since the issue is specific to arm64, revert back to memblock_reserve()'ing
> the UEFI memory map when running on arm64. This is a temporary fix for v4.5
> and v4.6, and will be superseded in the v4.7 timeframe when we will be able
> to move back to memblock_reserve() unconditionally.
> 
> Fixes: 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
> Reported-by: Mark Salter <msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  drivers/firmware/efi/arm-init.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> index aa1f743152a2..8714f8c271ba 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -203,7 +203,19 @@ void __init efi_init(void)
>  
>  	reserve_regions();
>  	early_memunmap(memmap.map, params.mmap_size);
> -	memblock_mark_nomap(params.mmap & PAGE_MASK,
> -			    PAGE_ALIGN(params.mmap_size +
> -				       (params.mmap & ~PAGE_MASK)));
> +
> +	if (IS_ENABLED(CONFIG_ARM)) {
> +		/*
> +		 * ARM currently does not allow ioremap_cache() to be called on
> +		 * memory regions that are covered by struct page. So remove the
> +		 * UEFI memory map from the linear mapping.
> +		 */
> +		memblock_mark_nomap(params.mmap & PAGE_MASK,
> +				    PAGE_ALIGN(params.mmap_size +
> +					       (params.mmap & ~PAGE_MASK)));
> +	} else {
> +		memblock_reserve(params.mmap & PAGE_MASK,
> +				 PAGE_ALIGN(params.mmap_size +
> +					    (params.mmap & ~PAGE_MASK)));
> +	}
>  }
> -- 
> 2.5.0
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Matt Fleming]

On Wed, 30 Mar, at 09:46:23AM, Ard Biesheuvel wrote:
> Hi Matt,
> 
> Could we queue this as a fix for v4.6 with a cc:stable for v4.5, please?
> (assuming no objections from any of the cc'ees)

Yep, I've picked this up. I'll go out to tip tomorrow.

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Steve Capper]

On 31 March 2016 at 21:35, Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> wrote:
> On Wed, 30 Mar, at 09:46:23AM, Ard Biesheuvel wrote:
>> Hi Matt,
>>
>> Could we queue this as a fix for v4.6 with a cc:stable for v4.5, please?
>> (assuming no objections from any of the cc'ees)
>
> Yep, I've picked this up. I'll go out to tip tomorrow.
>

Hello,
Is this going to make it in for 4.6?
I ran into this issue the other day, and can confirm that Ard's patch
is helpful.

Cheers,
-- 
Steve

> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Matt Fleming]

On Fri, 15 Apr, at 05:44:02PM, Steve Capper wrote:
> 
> Hello,
> Is this going to make it in for 4.6?
> I ran into this issue the other day, and can confirm that Ard's patch
> is helpful.

Good question.

Ingo did you send the patch in the last EFI urgent pull request to
Linus yet? I can find it in tip/efi-urgent-for-linus but not in Linus'
tree.

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Ingo Molnar]

* Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> wrote:

> On Fri, 15 Apr, at 05:44:02PM, Steve Capper wrote:
> > 
> > Hello,
> > Is this going to make it in for 4.6?
> > I ran into this issue the other day, and can confirm that Ard's patch
> > is helpful.
> 
> Good question.
> 
> Ingo did you send the patch in the last EFI urgent pull request to
> Linus yet? I can find it in tip/efi-urgent-for-linus but not in Linus'
> tree.

I just sent it to Linus.

It got delayed a bit because it had an x86/urgent dependency that had to be sent 
upstream first. (In the future you can avoid such delays by basing EFI urgent 
fixes on an upstream -rc kernel, not x86/urgent.)

Thanks,

	Ingo

Re: [PATCH] efi/arm64: don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Matt Fleming]

On Sat, 16 Apr, at 11:09:10AM, Ingo Molnar wrote:
> 
> I just sent it to Linus.
> 
> It got delayed a bit because it had an x86/urgent dependency that had to be sent 
> upstream first. (In the future you can avoid such delays by basing EFI urgent 
> fixes on an upstream -rc kernel, not x86/urgent.)

Noted. I'll do this in future, thanks Ingo.

[GIT PULL] EFI urgent fix

[Matt Fleming]

Folks,

Please pull the following fix for an arm64 boot crash reported by Mark
Salter with 64KB granule kernels. It is also tagged for stable.

The following changes since commit 591b1d8d86074ac3a3163d89bcfe7b232cf83902:

  x86/mm/pkeys: Add missing Documentation (2016-03-29 11:21:17 +0200)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi.git tags/efi-urgent

for you to fetch changes up to 7cc8cbcf82d165dd658d89a7a287140948e76413:

  efi/arm64: Don't apply MEMBLOCK_NOMAP to UEFI memory map mapping (2016-03-31 21:33:50 +0100)

----------------------------------------------------------------
 * Fix a boot crash on arm64 caused by a recent commit to mark the EFI
   memory map as 'MEMBLOCK_NOMAP' which causes the regions to be
   omitted from the kernel direct mapping - Ard Biesheuvel

----------------------------------------------------------------
Ard Biesheuvel (1):
      efi/arm64: Don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

 drivers/firmware/efi/arm-init.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

[PATCH] efi/arm64: Don't apply MEMBLOCK_NOMAP to UEFI memory map mapping

[Matt Fleming]

From: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Commit 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as
MEMBLOCK_NOMAP") updated the mapping logic of both the RuntimeServices
regions as well as the kernel's copy of the UEFI memory map to set the
MEMBLOCK_NOMAP flag, which causes these regions to be omitted from the
kernel direct mapping, and from being covered by a struct page.
For the RuntimeServices regions, this is an obvious win, since the contents
of these regions have significance to the firmware executable code itself,
and are mapped in the EFI page tables using attributes that are described in
the UEFI memory map, and which may differ from the attributes we use for
mapping system RAM. It also prevents the contents from being modified
inadvertently, since the EFI page tables are only live during runtime
service invocations.

None of these concerns apply to the allocation that covers the UEFI memory
map, since it is entirely owned by the kernel. Setting the MEMBLOCK_NOMAP on
the region did allow us to use ioremap_cache() to map it both on arm64 and
on ARM, since the latter does not allow ioremap_cache() to be used on
regions that are covered by a struct page.

The ioremap_cache() on ARM restriction will be lifted in the v4.7 timeframe,
but in the mean time, it has been reported that commit 4dffbfc48d65 causes
a regression on 64k granule kernels. This is due to the fact that, given
the 64 KB page size, the region that we end up removing from the kernel
direct mapping is rounded up to 64 KB, and this 64 KB page frame may be
shared with the initrd when booting via GRUB (which does not align its
EFI_LOADER_DATA allocations to 64 KB like the stub does). This will crash
the kernel as soon as it tries to access the initrd.

Since the issue is specific to arm64, revert back to memblock_reserve()'ing
the UEFI memory map when running on arm64. This is a temporary fix for v4.5
and v4.6, and will be superseded in the v4.7 timeframe when we will be able
to move back to memblock_reserve() unconditionally.

Fixes: 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
Reported-by: Mark Salter <msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Acked-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Cc: Leif Lindholm <leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
Cc: Jeremy Linton <jeremy.linton-5wv7dgnIgG8@public.gmane.org>
Cc: Mark Langsdorf <mlangsdo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> # v4.5
Signed-off-by: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
---
 drivers/firmware/efi/arm-init.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index aa1f743152a2..8714f8c271ba 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -203,7 +203,19 @@ void __init efi_init(void)
 
 	reserve_regions();
 	early_memunmap(memmap.map, params.mmap_size);
-	memblock_mark_nomap(params.mmap & PAGE_MASK,
-			    PAGE_ALIGN(params.mmap_size +
-				       (params.mmap & ~PAGE_MASK)));
+
+	if (IS_ENABLED(CONFIG_ARM)) {
+		/*
+		 * ARM currently does not allow ioremap_cache() to be called on
+		 * memory regions that are covered by struct page. So remove the
+		 * UEFI memory map from the linear mapping.
+		 */
+		memblock_mark_nomap(params.mmap & PAGE_MASK,
+				    PAGE_ALIGN(params.mmap_size +
+					       (params.mmap & ~PAGE_MASK)));
+	} else {
+		memblock_reserve(params.mmap & PAGE_MASK,
+				 PAGE_ALIGN(params.mmap_size +
+					    (params.mmap & ~PAGE_MASK)));
+	}
 }
-- 
2.7.3