linux-kernel - Re: [PATCH v3 2/2] x86/sev-es: Include XSS value in GHCB CPUID request

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Message-ID: <e0b0180f-17aa-444a-8ede-39709501e82b@intel.com>
Date: Wed, 24 Sep 2025 16:02:11 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: John Allen <john.allen@....com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org, seanjc@...gle.com,
 pbonzini@...hat.com
Cc: rick.p.edgecombe@...el.com, mlevitsk@...hat.com, weijiang.yang@...el.com,
 chao.gao@...el.com, bp@...en8.de, dave.hansen@...ux.intel.com,
 hpa@...or.com, mingo@...hat.com, tglx@...utronix.de, thomas.lendacky@....com
Subject: Re: [PATCH v3 2/2] x86/sev-es: Include XSS value in GHCB CPUID
 request

On 9/24/25 13:08, John Allen wrote:
> +	if (has_cpuflag(X86_FEATURE_SHSTK) && regs->ax == 0xd && regs->cx == 1) {
> +		struct msr m;
> +
> +		raw_rdmsr(MSR_IA32_XSS, &m);
> +		ghcb_set_xss(ghcb, m.q);
> +	}

Is there a reason this is open-coding CPUID_LEAF_XSTATE?