FAILED: patch "[PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with" failed to apply to 4.1-stable tree

FAILED: patch "[PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with" failed to apply to 4.1-stable tree

[gregkh]

The patch below does not apply to the 4.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From e13d918a19a7b6cba62b32884f5e336e764c2cc6 Mon Sep 17 00:00:00 2001
From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Date: Tue, 27 Oct 2015 17:29:10 +0000
Subject: [PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with
 extended idmap

Commit dd006da21646 ("arm64: mm: increase VA range of identity map")
introduced a mechanism to extend the virtual memory map range
to support arm64 systems with system RAM located at very high offset,
where the identity mapping used to enable/disable the MMU requires
additional translation levels to map the physical memory at an equal
virtual offset.

The kernel detects at boot time the tcr_el1.t0sz value required by the
identity mapping and sets-up the tcr_el1.t0sz register field accordingly,
any time the identity map is required in the kernel (ie when enabling the
MMU).

After enabling the MMU, in the cold boot path the kernel resets the
tcr_el1.t0sz to its default value (ie the actual configuration value for
the system virtual address space) so that after enabling the MMU the
memory space translated by ttbr0_el1 is restored as expected.

Commit dd006da21646 ("arm64: mm: increase VA range of identity map")
also added code to set-up the tcr_el1.t0sz value when the kernel resumes
from low-power states with the MMU off through cpu_resume() in order to
effectively use the identity mapping to enable the MMU but failed to add
the code required to restore the tcr_el1.t0sz to its default value, when
the core returns to the kernel with the MMU enabled, so that the kernel
might end up running with tcr_el1.t0sz value set-up for the identity
mapping which can be lower than the value required by the actual virtual
address space, resulting in an erroneous set-up.

This patchs adds code in the resume path that restores the tcr_el1.t0sz
default value upon core resume, mirroring this way the cold boot path
behaviour therefore fixing the issue.

Cc: <stable@vger.kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Fixes: dd006da21646 ("arm64: mm: increase VA range of identity map")
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 8297d502217e..44ca4143b013 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -80,17 +80,21 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
 	if (ret == 0) {
 		/*
 		 * We are resuming from reset with TTBR0_EL1 set to the
-		 * idmap to enable the MMU; restore the active_mm mappings in
-		 * TTBR0_EL1 unless the active_mm == &init_mm, in which case
-		 * the thread entered cpu_suspend with TTBR0_EL1 set to
-		 * reserved TTBR0 page tables and should be restored as such.
+		 * idmap to enable the MMU; set the TTBR0 to the reserved
+		 * page tables to prevent speculative TLB allocations, flush
+		 * the local tlb and set the default tcr_el1.t0sz so that
+		 * the TTBR0 address space set-up is properly restored.
+		 * If the current active_mm != &init_mm we entered cpu_suspend
+		 * with mappings in TTBR0 that must be restored, so we switch
+		 * them back to complete the address space configuration
+		 * restoration before returning.
 		 */
-		if (mm == &init_mm)
-			cpu_set_reserved_ttbr0();
-		else
-			cpu_switch_mm(mm->pgd, mm);
-
+		cpu_set_reserved_ttbr0();
 		flush_tlb_all();
+		cpu_set_default_tcr_t0sz();
+
+		if (mm != &init_mm)
+			cpu_switch_mm(mm->pgd, mm);
 
 		/*
 		 * Restore per-cpu offset before any kernel

Re: FAILED: patch "[PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with" failed to apply to 4.1-stable tree

[Lorenzo Pieralisi]

Hi Greg,

On Thu, Nov 05, 2015 at 09:57:12PM -0800, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.1-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

The reason for that is a dependency on commit id:

commit af391b15f7b5 ("arm64: kernel: rename __cpu_suspend to keep it
aligned with arm")

that was not sent to stable since it was not a fix.

I applied the commit above and subsequently the $SUBJECT patch on
top of v4.1, tested the resulting tree and everything is fine, so
if you can apply the dependency above and then this patch I think
we are done, please let me know if that's reasonable and you need
more help.

Thank you very much !
Lorenzo

> 
> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> From e13d918a19a7b6cba62b32884f5e336e764c2cc6 Mon Sep 17 00:00:00 2001
> From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Date: Tue, 27 Oct 2015 17:29:10 +0000
> Subject: [PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with
>  extended idmap
> 
> Commit dd006da21646 ("arm64: mm: increase VA range of identity map")
> introduced a mechanism to extend the virtual memory map range
> to support arm64 systems with system RAM located at very high offset,
> where the identity mapping used to enable/disable the MMU requires
> additional translation levels to map the physical memory at an equal
> virtual offset.
> 
> The kernel detects at boot time the tcr_el1.t0sz value required by the
> identity mapping and sets-up the tcr_el1.t0sz register field accordingly,
> any time the identity map is required in the kernel (ie when enabling the
> MMU).
> 
> After enabling the MMU, in the cold boot path the kernel resets the
> tcr_el1.t0sz to its default value (ie the actual configuration value for
> the system virtual address space) so that after enabling the MMU the
> memory space translated by ttbr0_el1 is restored as expected.
> 
> Commit dd006da21646 ("arm64: mm: increase VA range of identity map")
> also added code to set-up the tcr_el1.t0sz value when the kernel resumes
> from low-power states with the MMU off through cpu_resume() in order to
> effectively use the identity mapping to enable the MMU but failed to add
> the code required to restore the tcr_el1.t0sz to its default value, when
> the core returns to the kernel with the MMU enabled, so that the kernel
> might end up running with tcr_el1.t0sz value set-up for the identity
> mapping which can be lower than the value required by the actual virtual
> address space, resulting in an erroneous set-up.
> 
> This patchs adds code in the resume path that restores the tcr_el1.t0sz
> default value upon core resume, mirroring this way the cold boot path
> behaviour therefore fixing the issue.
> 
> Cc: <stable@vger.kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Fixes: dd006da21646 ("arm64: mm: increase VA range of identity map")
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Signed-off-by: James Morse <james.morse@arm.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> 
> diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
> index 8297d502217e..44ca4143b013 100644
> --- a/arch/arm64/kernel/suspend.c
> +++ b/arch/arm64/kernel/suspend.c
> @@ -80,17 +80,21 @@ int cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
>  	if (ret == 0) {
>  		/*
>  		 * We are resuming from reset with TTBR0_EL1 set to the
> -		 * idmap to enable the MMU; restore the active_mm mappings in
> -		 * TTBR0_EL1 unless the active_mm == &init_mm, in which case
> -		 * the thread entered cpu_suspend with TTBR0_EL1 set to
> -		 * reserved TTBR0 page tables and should be restored as such.
> +		 * idmap to enable the MMU; set the TTBR0 to the reserved
> +		 * page tables to prevent speculative TLB allocations, flush
> +		 * the local tlb and set the default tcr_el1.t0sz so that
> +		 * the TTBR0 address space set-up is properly restored.
> +		 * If the current active_mm != &init_mm we entered cpu_suspend
> +		 * with mappings in TTBR0 that must be restored, so we switch
> +		 * them back to complete the address space configuration
> +		 * restoration before returning.
>  		 */
> -		if (mm == &init_mm)
> -			cpu_set_reserved_ttbr0();
> -		else
> -			cpu_switch_mm(mm->pgd, mm);
> -
> +		cpu_set_reserved_ttbr0();
>  		flush_tlb_all();
> +		cpu_set_default_tcr_t0sz();
> +
> +		if (mm != &init_mm)
> +			cpu_switch_mm(mm->pgd, mm);
>  
>  		/*
>  		 * Restore per-cpu offset before any kernel
> 

Re: FAILED: patch "[PATCH] arm64: kernel: fix tcr_el1.t0sz restore on systems with" failed to apply to 4.1-stable tree

[Greg KH]

On Fri, Nov 06, 2015 at 03:32:54PM +0000, Lorenzo Pieralisi wrote:
> Hi Greg,
> 
> On Thu, Nov 05, 2015 at 09:57:12PM -0800, gregkh@linuxfoundation.org wrote:
> > 
> > The patch below does not apply to the 4.1-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@vger.kernel.org>.
> 
> The reason for that is a dependency on commit id:
> 
> commit af391b15f7b5 ("arm64: kernel: rename __cpu_suspend to keep it
> aligned with arm")
> 
> that was not sent to stable since it was not a fix.
> 
> I applied the commit above and subsequently the $SUBJECT patch on
> top of v4.1, tested the resulting tree and everything is fine, so
> if you can apply the dependency above and then this patch I think
> we are done, please let me know if that's reasonable and you need
> more help.

Thanks, that worked.

greg k-h