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
