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Message-ID: <27a14f56-3d5a-9d66-83be-e5893d5f0a9e@intel.com>
Date:   Wed, 9 Aug 2023 11:05:03 +0800
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Subject: Re: [PATCH v5 11/19] KVM:VMX: Emulate read and write to CET MSRs
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To:     Paolo Bonzini <pbonzini@redhat.com>
CC:     <rick.p.edgecombe@intel.com>, <chao.gao@intel.com>,
        <binbin.wu@linux.intel.com>, <seanjc@google.com>,
        <peterz@infradead.org>, <john.allen@amd.com>,
        <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20230803042732.88515-1-weijiang.yang@intel.com>
 <20230803042732.88515-12-weijiang.yang@intel.com>
 <b5c8d8cb-90c9-dff3-7f1c-e0f669950191@redhat.com>
From:   "Yang, Weijiang" <weijiang.yang@intel.com>
In-Reply-To: <b5c8d8cb-90c9-dff3-7f1c-e0f669950191@redhat.com>
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On 8/5/2023 5:40 AM, Paolo Bonzini wrote:
> On 8/3/23 06:27, Yang Weijiang wrote:
>> +        if (msr_info->index == MSR_KVM_GUEST_SSP)
>> +            msr_info->data = vmcs_readl(GUEST_SSP);
>
> Accesses to MSR_KVM_(GUEST_)SSP must be rejected unless host-initiated.
Yes, it's kept, in v5 it's folded in:

+static bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu,

+struct msr_data *msr)

+{

+if (is_shadow_stack_msr(msr->index)) {

+if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK))

+return false;

+

+if (msr->index == MSR_KVM_GUEST_SSP)

+return msr->host_initiated;

+

+return msr->host_initiated ||

+guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);

+}

+

+if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&

+!kvm_cpu_cap_has(X86_FEATURE_IBT))

+return false;

+

+return msr->host_initiated ||

+guest_cpuid_has(vcpu, X86_FEATURE_IBT) ||

+guest_cpuid_has(vcpu, X86_FEATURE_SHSTK); }

+

> Paolo
>