2020-12-22 07:12:52

by Christophe Leroy

Subject: [PATCH] powerpc/32s: Fix RTAS machine check with VMAP stack

When we have VMAP stack, exception prolog 1 sets r1, not r11.

Fixes: da7bb43ab9da ("powerpc/32: Fix vmap stack - Properly set r1 before activating MMU")
Fixes: d2e006036082 ("powerpc/32: Use SPRN_SPRG_SCRATCH2 in exception prologs")
Cc: [email protected]
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/head_book3s_32.S | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 349bf3f0c3af..fbc48a500846 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -260,9 +260,16 @@ __secondary_hold_acknowledge:
MachineCheck:
EXCEPTION_PROLOG_0
#ifdef CONFIG_PPC_CHRP
+#ifdef CONFIG_VMAP_STACK
+ mtspr SPRN_SPRG_SCRATCH2,r1
+ mfspr r1, SPRN_SPRG_THREAD
+ lwz r1, RTAS_SP(r1)
+ cmpwi cr1, r1, 0
+#else
mfspr r11, SPRN_SPRG_THREAD
lwz r11, RTAS_SP(r11)
cmpwi cr1, r11, 0
+#endif
bne cr1, 7f
#endif /* CONFIG_PPC_CHRP */
EXCEPTION_PROLOG_1 for_rtas=1
--
2.25.0

2020-12-22 13:16:06

by Michael Ellerman

Subject: Re: [PATCH] powerpc/32s: Fix RTAS machine check with VMAP stack

On Tue, 22 Dec 2020 07:11:18 +0000 (UTC), Christophe Leroy wrote:
> When we have VMAP stack, exception prolog 1 sets r1, not r11.

Applied to powerpc/fixes.

[1/1] powerpc/32s: Fix RTAS machine check with VMAP stack
https://git.kernel.org/powerpc/c/9c7422b92cb27369653c371ad9c44a502e5eea8f

cheers

2020-12-23 06:50:41

by Christophe Leroy

Subject: Re: [PATCH] powerpc/32s: Fix RTAS machine check with VMAP stack

Le 22/12/2020 à 08:11, Christophe Leroy a écrit :
> When we have VMAP stack, exception prolog 1 sets r1, not r11.

But exception prolog 1 uses r1 to setup r1 when machine check happens in kernel.
So r1 must be restored when the branch is not taken. See subsequent patch I just sent out.

Christophe

>
> Fixes: da7bb43ab9da ("powerpc/32: Fix vmap stack - Properly set r1 before activating MMU")
> Fixes: d2e006036082 ("powerpc/32: Use SPRN_SPRG_SCRATCH2 in exception prologs")
> Cc: [email protected]
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> arch/powerpc/kernel/head_book3s_32.S | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
> index 349bf3f0c3af..fbc48a500846 100644
> --- a/arch/powerpc/kernel/head_book3s_32.S
> +++ b/arch/powerpc/kernel/head_book3s_32.S
> @@ -260,9 +260,16 @@ __secondary_hold_acknowledge:
> MachineCheck:
> EXCEPTION_PROLOG_0
> #ifdef CONFIG_PPC_CHRP
> +#ifdef CONFIG_VMAP_STACK
> + mtspr SPRN_SPRG_SCRATCH2,r1
> + mfspr r1, SPRN_SPRG_THREAD
> + lwz r1, RTAS_SP(r1)
> + cmpwi cr1, r1, 0
> +#else
> mfspr r11, SPRN_SPRG_THREAD
> lwz r11, RTAS_SP(r11)
> cmpwi cr1, r11, 0
> +#endif
> bne cr1, 7f
> #endif /* CONFIG_PPC_CHRP */
> EXCEPTION_PROLOG_1 for_rtas=1
>

2020-12-24 01:07:26

by Michael Ellerman

Subject: Re: [PATCH] powerpc/32s: Fix RTAS machine check with VMAP stack

Christophe Leroy <[email protected]> writes:
> Le 22/12/2020 à 08:11, Christophe Leroy a écrit :
>> When we have VMAP stack, exception prolog 1 sets r1, not r11.
>
> But exception prolog 1 uses r1 to setup r1 when machine check happens in kernel.
> So r1 must be restored when the branch is not taken. See subsequent patch I just sent out.

OK. This is still on the tip of fixes, so I'll rewind it to drop this
commit, and then apply this and the fixup as one patch next week.

cheers