linux-kernel - Re: [PATCH v11 20/20] x86/cpu/amd: Do not print FW

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Message-ID: <ad654a7b-47fd-c7a4-7d79-46f4393e9640@amd.com>
Date: Fri, 13 Sep 2024 12:21:23 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
 bp@...en8.de, x86@...nel.org, kvm@...r.kernel.org
Cc: mingo@...hat.com, tglx@...utronix.de, dave.hansen@...ux.intel.com,
 pgonda@...gle.com, seanjc@...gle.com, pbonzini@...hat.com
Subject: Re: [PATCH v11 20/20] x86/cpu/amd: Do not print FW_BUG for Secure TSC

On 7/31/24 10:08, Nikunj A Dadhania wrote:
> When Secure TSC is enabled and TscInvariant (bit 8) in CPUID_8000_0007_edx
> is set, the kernel complains with the below firmware bug:
> 
> [Firmware Bug]: TSC doesn't count with P0 frequency!
> 
> Secure TSC does not need to run at P0 frequency; the TSC frequency is set
> by the VMM as part of the SNP_LAUNCH_START command. Skip this check when
> Secure TSC is enabled
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@....com>
> Tested-by: Peter Gonda <pgonda@...gle.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/kernel/cpu/amd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index be5889bded49..87b55d2183a0 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -370,7 +370,8 @@ static void bsp_determine_snp(struct cpuinfo_x86 *c)
>  
>  static void bsp_init_amd(struct cpuinfo_x86 *c)
>  {
> -	if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {
> +	if (cpu_has(c, X86_FEATURE_CONSTANT_TSC) &&
> +	    !cc_platform_has(CC_ATTR_GUEST_SECURE_TSC)) {
>  
>  		if (c->x86 > 0x10 ||
>  		    (c->x86 == 0x10 && c->x86_model >= 0x2)) {