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Message-ID: <c5bdcd8e-c6cd-d586-499c-4a2b7528cda9@redhat.com>
Date: Fri, 4 Aug 2023 23:45:13 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>,
Chao Gao <chao.gao@...el.com>
Cc: Yang Weijiang <weijiang.yang@...el.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 v5 11/19] KVM:VMX: Emulate read and write to CET MSRs
On 8/4/23 23:27, Sean Christopherson wrote:
>>> +
>>> + 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);
>
> Similar to my suggestsion for XSS, I think we drop the waiver for host_initiated
> accesses, i.e. require the feature to be enabled and exposed to the guest, even
> for the host.
No, please don't. Allowing host-initiated accesses is what makes it
possible to take the list of MSR indices and pass it blindly to
KVM_GET_MSR and KVM_SET_MSR. This should be documented, will send a patch.
Paolo
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