[PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK

[PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK

[Christophe Leroy]

When CONFIG_PROVE_LOCKING is selected together with (now default)
CONFIG_VMAP_STACK, kernel enter deadlock during boot.

At the point of checking whether interrupts are enabled or not, the
value of MSR saved on stack is read using the physical address of the
stack. But at this point, when using VMAP stack the DATA MMU
translation has already been re-enabled, leading to deadlock.

Don't use the physical address of the stack when
CONFIG_VMAP_STACK is set.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")
---
 arch/powerpc/kernel/entry_32.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 77abbc34bbe0..0713daa651d9 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -214,7 +214,7 @@ transfer_to_handler_cont:
 	 * To speed up the syscall path where interrupts stay on, let's check
 	 * first if we are changing the MSR value at all.
 	 */
-	tophys(r12, r1)
+	tophys_novmstack r12, r1
 	lwz	r12,_MSR(r12)
 	andi.	r12,r12,MSR_EE
 	bne	1f
-- 
2.25.0

Re: [PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK

[Guenter Roeck]

On Fri, Feb 07, 2020 at 05:20:57PM +0000, Christophe Leroy wrote:
> When CONFIG_PROVE_LOCKING is selected together with (now default)
> CONFIG_VMAP_STACK, kernel enter deadlock during boot.
> 
> At the point of checking whether interrupts are enabled or not, the
> value of MSR saved on stack is read using the physical address of the
> stack. But at this point, when using VMAP stack the DATA MMU
> translation has already been re-enabled, leading to deadlock.
> 
> Don't use the physical address of the stack when
> CONFIG_VMAP_STACK is set.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")

Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  arch/powerpc/kernel/entry_32.S | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 77abbc34bbe0..0713daa651d9 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -214,7 +214,7 @@ transfer_to_handler_cont:
>  	 * To speed up the syscall path where interrupts stay on, let's check
>  	 * first if we are changing the MSR value at all.
>  	 */
> -	tophys(r12, r1)
> +	tophys_novmstack r12, r1
>  	lwz	r12,_MSR(r12)
>  	andi.	r12,r12,MSR_EE
>  	bne	1f
> -- 
> 2.25.0
> 

Re: [PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK

[Michael Ellerman]

On Fri, 2020-02-07 at 17:20:57 UTC, Christophe Leroy wrote:
> When CONFIG_PROVE_LOCKING is selected together with (now default)
> CONFIG_VMAP_STACK, kernel enter deadlock during boot.
> 
> At the point of checking whether interrupts are enabled or not, the
> value of MSR saved on stack is read using the physical address of the
> stack. But at this point, when using VMAP stack the DATA MMU
> translation has already been re-enabled, leading to deadlock.
> 
> Don't use the physical address of the stack when
> CONFIG_VMAP_STACK is set.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/d4bf905307a1c90a27714ff7a9fd29b0a2ceed98

cheers