* [PATCH] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()
@ 2022-05-09 20:23 ` Alexander Graf
0 siblings, 0 replies; 4+ messages in thread
From: Alexander Graf @ 2022-05-09 20:23 UTC (permalink / raw)
To: kvm
Cc: linuxppc-dev, linux-kernel, Christophe Leroy, Paul Mackerras,
Benjamin Herrenschmidt, Michael Ellerman, Matt Evans, stable
Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
moved the switch_mmu_context() to C. While in principle a good idea, it
meant that the function now uses the stack. The stack is not accessible
from real mode though.
So to keep calling the function, let's turn on MSR_DR while we call it.
That way, all pointer references to the stack are handled virtually.
Reported-by: Matt Evans <matt@ozlabs.org>
Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
Signed-off-by: Alexander Graf <graf@amazon.com>
Cc: stable@vger.kernel.org
---
arch/powerpc/kvm/book3s_32_sr.S | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
index e3ab9df6cf19..bd4f798f7a46 100644
--- a/arch/powerpc/kvm/book3s_32_sr.S
+++ b/arch/powerpc/kvm/book3s_32_sr.S
@@ -122,11 +122,21 @@
/* 0x0 - 0xb */
- /* 'current->mm' needs to be in r4 */
- tophys(r4, r2)
- lwz r4, MM(r4)
- tophys(r4, r4)
- /* This only clobbers r0, r3, r4 and r5 */
+ /* switch_mmu_context() needs paging, let's enable it */
+ mfmsr r9
+ ori r11, r9, MSR_DR
+ mtmsr r11
+ sync
+
+ /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
+ lwz r4, MM(r2)
bl switch_mmu_context
+ /* Disable paging again */
+ mfmsr r9
+ li r6, MSR_DR
+ andc r9, r9, r6
+ mtmsr r9
+ sync
+
.endm
--
2.28.0.394.ge197136389
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()
@ 2022-05-09 20:23 ` Alexander Graf
0 siblings, 0 replies; 4+ messages in thread
From: Alexander Graf @ 2022-05-09 20:23 UTC (permalink / raw)
To: kvm; +Cc: Matt Evans, linux-kernel, Paul Mackerras, stable, linuxppc-dev
Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
moved the switch_mmu_context() to C. While in principle a good idea, it
meant that the function now uses the stack. The stack is not accessible
from real mode though.
So to keep calling the function, let's turn on MSR_DR while we call it.
That way, all pointer references to the stack are handled virtually.
Reported-by: Matt Evans <matt@ozlabs.org>
Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
Signed-off-by: Alexander Graf <graf@amazon.com>
Cc: stable@vger.kernel.org
---
arch/powerpc/kvm/book3s_32_sr.S | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
index e3ab9df6cf19..bd4f798f7a46 100644
--- a/arch/powerpc/kvm/book3s_32_sr.S
+++ b/arch/powerpc/kvm/book3s_32_sr.S
@@ -122,11 +122,21 @@
/* 0x0 - 0xb */
- /* 'current->mm' needs to be in r4 */
- tophys(r4, r2)
- lwz r4, MM(r4)
- tophys(r4, r4)
- /* This only clobbers r0, r3, r4 and r5 */
+ /* switch_mmu_context() needs paging, let's enable it */
+ mfmsr r9
+ ori r11, r9, MSR_DR
+ mtmsr r11
+ sync
+
+ /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
+ lwz r4, MM(r2)
bl switch_mmu_context
+ /* Disable paging again */
+ mfmsr r9
+ li r6, MSR_DR
+ andc r9, r9, r6
+ mtmsr r9
+ sync
+
.endm
--
2.28.0.394.ge197136389
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()
2022-05-09 20:23 ` Alexander Graf
@ 2022-05-10 10:33 ` Matt Evans
-1 siblings, 0 replies; 4+ messages in thread
From: Matt Evans @ 2022-05-10 10:33 UTC (permalink / raw)
To: Alexander Graf
Cc: kvm, linuxppc-dev, linux-kernel, Christophe Leroy,
Paul Mackerras, Ben Herrenschmitt, Michael Ellerman, stable
Hi Alex,
> On 9 May 2022, at 21:23, Alexander Graf <graf@amazon.com> wrote:
>
> Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
> moved the switch_mmu_context() to C. While in principle a good idea, it
> meant that the function now uses the stack. The stack is not accessible
> from real mode though.
>
> So to keep calling the function, let's turn on MSR_DR while we call it.
> That way, all pointer references to the stack are handled virtually.
>
> Reported-by: Matt Evans <matt@ozlabs.org>
> Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
> Signed-off-by: Alexander Graf <graf@amazon.com>
> Cc: stable@vger.kernel.org
Many thanks - this addresses the issue I saw, and has been...
Tested-by: Matt Evans <matt@ozlabs.org>
...on a G4 host. One comment though:
> —
> arch/powerpc/kvm/book3s_32_sr.S | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
> index e3ab9df6cf19..bd4f798f7a46 100644
> --- a/arch/powerpc/kvm/book3s_32_sr.S
> +++ b/arch/powerpc/kvm/book3s_32_sr.S
> @@ -122,11 +122,21 @@
>
> /* 0x0 - 0xb */
>
> - /* 'current->mm' needs to be in r4 */
> - tophys(r4, r2)
> - lwz r4, MM(r4)
> - tophys(r4, r4)
> - /* This only clobbers r0, r3, r4 and r5 */
> + /* switch_mmu_context() needs paging, let's enable it */
> + mfmsr r9
> + ori r11, r9, MSR_DR
> + mtmsr r11
> + sync
> +
> + /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
> + lwz r4, MM(r2)
> bl switch_mmu_context
Of the volatile registers, I believe r12 is still valuable here and would need to be preserved.
(I can’t spot any others but would defer to your judgement here.)
For example:
diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
index e3ab9df6cf19..41fc9ca12d38 100644
--- a/arch/powerpc/kvm/book3s_32_sr.S
+++ b/arch/powerpc/kvm/book3s_32_sr.S
@@ -122,11 +122,23 @@
/* 0x0 - 0xb */
- /* 'current->mm' needs to be in r4 */
- tophys(r4, r2)
- lwz r4, MM(r4)
- tophys(r4, r4)
- /* This only clobbers r0, r3, r4 and r5 */
+ /* switch_mmu_context() needs paging, let's enable it */
+ mfmsr r9
+ ori r11, r9, MSR_DR
+ mtmsr r11
+ sync
+
+ SAVE_GPR(12, r1)
+ /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
+ lwz r4, MM(r2)
bl switch_mmu_context
+ REST_GPR(12, r1)
+
+ /* Disable paging again */
+ mfmsr r9
+ li r6, MSR_DR
+ andc r9, r9, r6
+ mtmsr r9
+ sync
.endm
Matt
>
> + /* Disable paging again */
> + mfmsr r9
> + li r6, MSR_DR
> + andc r9, r9, r6
> + mtmsr r9
> + sync
> +
> .endm
> --
> 2.28.0.394.ge197136389
>
>
>
>
> Amazon Development Center Germany GmbH
> Krausenstr. 38
> 10117 Berlin
> Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
> Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
> Sitz: Berlin
> Ust-ID: DE 289 237 879
>
>
>
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context()
@ 2022-05-10 10:33 ` Matt Evans
0 siblings, 0 replies; 4+ messages in thread
From: Matt Evans @ 2022-05-10 10:33 UTC (permalink / raw)
To: Alexander Graf; +Cc: kvm, linux-kernel, Paul Mackerras, stable, linuxppc-dev
Hi Alex,
> On 9 May 2022, at 21:23, Alexander Graf <graf@amazon.com> wrote:
>
> Commit 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
> moved the switch_mmu_context() to C. While in principle a good idea, it
> meant that the function now uses the stack. The stack is not accessible
> from real mode though.
>
> So to keep calling the function, let's turn on MSR_DR while we call it.
> That way, all pointer references to the stack are handled virtually.
>
> Reported-by: Matt Evans <matt@ozlabs.org>
> Fixes: 863771a28e27 ("powerpc/32s: Convert switch_mmu_context() to C")
> Signed-off-by: Alexander Graf <graf@amazon.com>
> Cc: stable@vger.kernel.org
Many thanks - this addresses the issue I saw, and has been...
Tested-by: Matt Evans <matt@ozlabs.org>
...on a G4 host. One comment though:
> —
> arch/powerpc/kvm/book3s_32_sr.S | 20 +++++++++++++++-----
> 1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
> index e3ab9df6cf19..bd4f798f7a46 100644
> --- a/arch/powerpc/kvm/book3s_32_sr.S
> +++ b/arch/powerpc/kvm/book3s_32_sr.S
> @@ -122,11 +122,21 @@
>
> /* 0x0 - 0xb */
>
> - /* 'current->mm' needs to be in r4 */
> - tophys(r4, r2)
> - lwz r4, MM(r4)
> - tophys(r4, r4)
> - /* This only clobbers r0, r3, r4 and r5 */
> + /* switch_mmu_context() needs paging, let's enable it */
> + mfmsr r9
> + ori r11, r9, MSR_DR
> + mtmsr r11
> + sync
> +
> + /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
> + lwz r4, MM(r2)
> bl switch_mmu_context
Of the volatile registers, I believe r12 is still valuable here and would need to be preserved.
(I can’t spot any others but would defer to your judgement here.)
For example:
diff --git a/arch/powerpc/kvm/book3s_32_sr.S b/arch/powerpc/kvm/book3s_32_sr.S
index e3ab9df6cf19..41fc9ca12d38 100644
--- a/arch/powerpc/kvm/book3s_32_sr.S
+++ b/arch/powerpc/kvm/book3s_32_sr.S
@@ -122,11 +122,23 @@
/* 0x0 - 0xb */
- /* 'current->mm' needs to be in r4 */
- tophys(r4, r2)
- lwz r4, MM(r4)
- tophys(r4, r4)
- /* This only clobbers r0, r3, r4 and r5 */
+ /* switch_mmu_context() needs paging, let's enable it */
+ mfmsr r9
+ ori r11, r9, MSR_DR
+ mtmsr r11
+ sync
+
+ SAVE_GPR(12, r1)
+ /* Calling switch_mmu_context(<inv>, current->mm, <inv>); */
+ lwz r4, MM(r2)
bl switch_mmu_context
+ REST_GPR(12, r1)
+
+ /* Disable paging again */
+ mfmsr r9
+ li r6, MSR_DR
+ andc r9, r9, r6
+ mtmsr r9
+ sync
.endm
Matt
>
> + /* Disable paging again */
> + mfmsr r9
> + li r6, MSR_DR
> + andc r9, r9, r6
> + mtmsr r9
> + sync
> +
> .endm
> --
> 2.28.0.394.ge197136389
>
>
>
>
> Amazon Development Center Germany GmbH
> Krausenstr. 38
> 10117 Berlin
> Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
> Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
> Sitz: Berlin
> Ust-ID: DE 289 237 879
>
>
>
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-05-10 10:34 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2022-05-09 20:23 [PATCH] KVM: PPC: Book3S PR: Enable MSR_DR for switch_mmu_context() Alexander Graf
2022-05-09 20:23 ` Alexander Graf
2022-05-10 10:33 ` Matt Evans
2022-05-10 10:33 ` Matt Evans
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