linux-kernel - Re: [PATCH v4 18/20] KVM:x86: Enable guest CET supervisor xstate bit support

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Date:   Thu, 27 Jul 2023 16:03:21 +0800
From:   Chao Gao <chao.gao@...el.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
CC:     <seanjc@...gle.com>, <pbonzini@...hat.com>, <peterz@...radead.org>,
        <john.allen@....com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <rick.p.edgecombe@...el.com>,
        <binbin.wu@...ux.intel.com>
Subject: Re: [PATCH v4 18/20] KVM:x86: Enable guest CET supervisor xstate bit
 support

On Thu, Jul 20, 2023 at 11:03:50PM -0400, Yang Weijiang wrote:
> 
> u64 __read_mostly host_efer;
> EXPORT_SYMBOL_GPL(host_efer);
>@@ -9638,6 +9639,7 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
> 	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
> 		rdmsrl(MSR_IA32_XSS, host_xss);
> 		kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;

>+		kvm_caps.supported_xss |= XFEATURE_MASK_CET_KERNEL;

Hardware may not support S_CET state management via XSAVES. we need to
consult CPUID.0xD.1[bit12].