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AFNElJ82sH9EVzkwYSnoc0XnkHv6pZkSF5LtPH5K8SKEa9PiMXLjChpBwk+Uu4StxJnvX5RPqMs=@vger.kernel.org X-Gm-Message-State: AOJu0YyfoUl8PHsdJC7J/XZZC5vJ7nLr8eJB7FFTVr9dbHzEfprZGJSJ rU2oH8WXw81cgMw9mDM2SpadeBOM3JpsAuFPc8/kj4b8VHdfnddc59/sCBWtbChB1daG8oyzZKk 4HHvRjQ== X-Received: from pgbg32.prod.google.com ([2002:a63:5220:0:b0:c76:3f60:53ff]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a20:3d96:b0:3a2:f14a:4277 with SMTP id adf61e73a8af0-3b411e1090dmr259151637.32.1780012813048; Thu, 28 May 2026 17:00:13 -0700 (PDT) Date: Thu, 28 May 2026 17:00:12 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: Message-ID: Subject: Re: [PATCH v3 3/4] KVM: x86: Virtualize AMD CPUID faulting From: Sean Christopherson To: Christian Ludloff Cc: Jim Mattson , David Kaplan , "pbonzini@redhat.com" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "hpa@zytor.com" , "shuah@kernel.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-kselftest@vger.kernel.org, "ctpence@google.com" Content-Type: text/plain; charset="us-ascii" On Thu, May 28, 2026, Christian Ludloff wrote: > > It appears it was a deliberate decision, due in part to the fact that the > > traditional flow of checking CPL exceptions before intercepts typically > > applies to using instructions in an illegal way, but the user is not doing > > anything illegal here by executing CPUID which is normally a legal > > instruction at CPL3. > > > > That said, clearly the behavior is different now between the vendors, > > however at this point the feedback I got is that our architects want to > > stick with the existing behavior unless there is a strong reason that it is > > a problem for SW. > > What is a HV expected to do for such a CPUID guest exit? Emulate hardware behavior. The only question we had was whether the observed hardware behavior (VM-Exit takes precedence over #GP) was AMD's architectural behavior.