linux-kernel - Re: [PATCH v15 06/13] x86/sev: Prevent GUEST_TSC_FREQ MSR interception for Secure TSC enabled guests

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Message-ID: <20250102145431.GAZ3aop4Z1NOakZ9KO@fat_crate.local>
Date: Thu, 2 Jan 2025 15:54:31 +0100
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: "Nikunj A. Dadhania" <nikunj@....com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, kvm@...r.kernel.org, mingo@...hat.com,
	tglx@...utronix.de, dave.hansen@...ux.intel.com, pgonda@...gle.com,
	seanjc@...gle.com, pbonzini@...hat.com
Subject: Re: [PATCH v15 06/13] x86/sev: Prevent GUEST_TSC_FREQ MSR
 interception for Secure TSC enabled guests

On Thu, Jan 02, 2025 at 08:45:36AM -0600, Tom Lendacky wrote:
> >> @@ -1477,7 +1477,9 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
> >>  	case MSR_IA32_TSC:
> >>  	case MSR_AMD64_GUEST_TSC_FREQ:
> >>  		if (sev_status & MSR_AMD64_SNP_SECURE_TSC)
> >> -			return __vc_handle_msr_tsc(regs, write);
> >> +			return __vc_handle_secure_tsc_msrs(regs, write);
> >> +		else
> >> +			break;
> 
> There's a return as part of the if, so no reason for the else. Just put
> the break in the normal place and it reads much clearer.

I guess that's in the eye of the beholder. I prefer a balanced

	if
		foo
	else
		bar

as it is as obvious and clear as it gets. Especially if it is interwoven in
a switch-case like here.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette