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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/19/24 03:40, Sean Christopherson wrote: > On Wed, 11 Dec 2024 09:29:52 -0800, Sean Christopherson wrote: >> Drop KVM's arbitrary behavior of making DE_CFG.LFENCE_SERIALIZE read-only >> for the guest, as rejecting writes can lead to guest crashes, e.g. Windows >> in particular doesn't gracefully handle unexpected #GPs on the WRMSR, and >> nothing in the AMD manuals suggests that LFENCE_SERIALIZE is read-only _if >> it exists_. >> >> KVM only allows LFENCE_SERIALIZE to be set, by the guest or host, if the >> underlying CPU has X86_FEATURE_LFENCE_RDTSC, i.e. if LFENCE is guaranteed >> to be serializing. So if the guest sets LFENCE_SERIALIZE, KVM will provide >> the desired/correct behavior without any additional action (the guest's >> value is never stuffed into hardware). And having LFENCE be serializing >> even when it's not _required_ to be is a-ok from a functional perspective. >> >> [...] > > Applied to kvm-x86 fixes, thanks! > > [1/1] KVM: SVM: Allow guest writes to set MSR_AMD64_DE_CFG bits > https://github.com/kvm-x86/linux/commit/2778c9a4687d Oh, I missed this! I assume you're going to send me a pull request today or tomorrow? Paolo