| Message ID | 20231018194104.1896415-3-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: nSVM: TLB_CONTROL / FLUSHBYASID "fixes" | expand |
On Wed, 2023-10-18 at 12:41 -0700, Sean Christopherson wrote: > Advertise support for FLUSHBYASID when nested SVM is enabled, as KVM can > always emulate flushing TLB entries for a vmcb12 ASID, e.g. by running L2 > with a new, fresh ASID in vmcb02. Some modern hypervisors, e.g. VMWare > Workstation 17, require FLUSHBYASID support and will refuse to run if it's > not present. > > Punt on proper support, as "Honor L1's request to flush an ASID on nested > VMRUN" is one of the TODO items in the (incomplete) list of issues that > need to be addressed in order for KVM to NOT do a full TLB flush on every > nested SVM transition (see nested_svm_transition_tlb_flush()). > > Reported-by: Stefan Sterz <s.sterz@proxmox.com> > Closes: https://lkml.kernel.org/r/b9915c9c-4cf6-051a-2d91-44cc6380f455%40proxmox.com > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/svm/svm.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 1785de7dc98b..9cf7eef161ff 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -5083,6 +5083,7 @@ static __init void svm_set_cpu_caps(void) > if (nested) { > kvm_cpu_cap_set(X86_FEATURE_SVM); > kvm_cpu_cap_set(X86_FEATURE_VMCBCLEAN); > + kvm_cpu_cap_set(X86_FEATURE_FLUSHBYASID); > > if (nrips) > kvm_cpu_cap_set(X86_FEATURE_NRIPS); Nitpick: if you think that this is worth it, maybe we can add a comment here on why we can 'support' the flushbyasid feature? in addition to the commit message. Other than that: Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Best regards, Maxim Levitsky
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 1785de7dc98b..9cf7eef161ff 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5083,6 +5083,7 @@ static __init void svm_set_cpu_caps(void) if (nested) { kvm_cpu_cap_set(X86_FEATURE_SVM); kvm_cpu_cap_set(X86_FEATURE_VMCBCLEAN); + kvm_cpu_cap_set(X86_FEATURE_FLUSHBYASID); if (nrips) kvm_cpu_cap_set(X86_FEATURE_NRIPS);
Advertise support for FLUSHBYASID when nested SVM is enabled, as KVM can always emulate flushing TLB entries for a vmcb12 ASID, e.g. by running L2 with a new, fresh ASID in vmcb02. Some modern hypervisors, e.g. VMWare Workstation 17, require FLUSHBYASID support and will refuse to run if it's not present. Punt on proper support, as "Honor L1's request to flush an ASID on nested VMRUN" is one of the TODO items in the (incomplete) list of issues that need to be addressed in order for KVM to NOT do a full TLB flush on every nested SVM transition (see nested_svm_transition_tlb_flush()). Reported-by: Stefan Sterz <s.sterz@proxmox.com> Closes: https://lkml.kernel.org/r/b9915c9c-4cf6-051a-2d91-44cc6380f455%40proxmox.com Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/svm/svm.c | 1 + 1 file changed, 1 insertion(+)