linux-kernel - Re: [PATCH v2] x86/mtrr: Check if fixed MTRRs exist before saving them

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Date: Wed, 28 Feb 2024 08:52:01 -0800
From: Andi Kleen <ak@...ux.intel.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86/mtrr: Check if fixed MTRRs exist before saving
 them

On Wed, Jan 10, 2024 at 07:08:06AM -0800, Andi Kleen wrote:
> This one place forgot to check the fixed capability. Otherwise there
> will a harmless but ugly WARN_ON for the failed WRMSR when the MSR
> doesn't exist. Noticed when testing X86S support.
> 
> Fixes: 2b1f6278d77c ("[PATCH] x86: Save the MTRRs of the BSP before")
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> ---
> 
> v2: Add Fixes tag and expand description.

Just wanted to ping the patch. Thanks.

-Andi


> ---
>  arch/x86/kernel/cpu/mtrr/mtrr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
> index 767bf1c71aad..2a2fc14955cd 100644
> --- a/arch/x86/kernel/cpu/mtrr/mtrr.c
> +++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
> @@ -609,7 +609,7 @@ void mtrr_save_state(void)
>  {
>  	int first_cpu;
>  
> -	if (!mtrr_enabled())
> +	if (!mtrr_enabled() || !mtrr_state.have_fixed)
>  		return;
>  
>  	first_cpu = cpumask_first(cpu_online_mask);
> -- 
> 2.43.0
>