linux-kernel - Re: [PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP

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Message-ID: <20200207173839.GA8313@roeck-us.net>
Date:   Fri, 7 Feb 2020 09:38:39 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK

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@....fr>
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Fixes: 028474876f47 ("powerpc/32: prepare for CONFIG_VMAP_STACK")

Tested-by: Guenter Roeck <linux@...ck-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
>