linux-kernel - Re: [PATCH 05/16] x86/sev: Move check for SNP Secure TSC support to tsc_early

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Message-ID: <85v7tq5d47.fsf@amd.com>
Date: Tue, 4 Feb 2025 08:27:04 +0000
From: Nikunj A Dadhania <nikunj@....com>
To: Sean Christopherson <seanjc@...gle.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Juergen Gross
	<jgross@...e.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang
	<haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
	<decui@...rosoft.com>, Ajay Kaher <ajay.kaher@...adcom.com>, "Alexey
 Makhalov" <alexey.amakhalov@...adcom.com>, Jan Kiszka
	<jan.kiszka@...mens.com>, Paolo Bonzini <pbonzini@...hat.com>, "Andy
 Lutomirski" <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>
CC: <linux-kernel@...r.kernel.org>, <linux-coco@...ts.linux.dev>,
	<virtualization@...ts.linux.dev>, <linux-hyperv@...r.kernel.org>,
	<jailhouse-dev@...glegroups.com>, <kvm@...r.kernel.org>,
	<xen-devel@...ts.xenproject.org>, Sean Christopherson <seanjc@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH 05/16] x86/sev: Move check for SNP Secure TSC support to
 tsc_early_init()

Sean Christopherson <seanjc@...gle.com> writes:

> Move the check on having a Secure TSC to the common tsc_early_init() so
> that it's obvious that having a Secure TSC is conditional, and to prepare
> for adding TDX to the mix (blindly initializing *both* SNP and TDX TSC
> logic looks especially weird).

Agree.

>
> No functional change intended.
>
> Cc: Nikunj A Dadhania <nikunj@....com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Nikunj A Dadhania <nikunj@....com>

> ---
>  arch/x86/coco/sev/core.c | 3 ---
>  arch/x86/kernel/tsc.c    | 3 ++-
>  2 files changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index e6ce4ca72465..dab386f782ce 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -3284,9 +3284,6 @@ void __init snp_secure_tsc_init(void)
>  {
>  	unsigned long long tsc_freq_mhz;
>  
> -	if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
> -		return;
> -
>  	setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
>  	setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
>  
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index 5a16271b7a5c..09ca0cbd4f31 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -1514,7 +1514,8 @@ void __init tsc_early_init(void)
>  	if (is_early_uv_system())
>  		return;
>  
> -	snp_secure_tsc_init();
> +	if (cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
> +		snp_secure_tsc_init();
>  
>  	if (!determine_cpu_tsc_frequencies(true))
>  		return;
> -- 
> 2.48.1.362.g079036d154-goog