On Thu, Dec 19, 2024, Paolo Bonzini wrote: > 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? Yep, I'll get it to you today.
