On Fri, Jan 30, 2026 at 3:41 PM Yosry Ahmed <[email protected]> wrote: > > January 30, 2026 at 3:30 PM, "Jim Mattson" <[email protected]> wrote: > > > > > > On Fri, Jan 30, 2026 at 7:26 AM Yosry Ahmed <[email protected]> wrote: > > > > > > > > On Thu, Jan 29, 2026 at 03:28:08PM -0800, Jim Mattson wrote: > > > Add amd_pmu_refresh_host_guest_eventsel_hw() to recalculate eventsel_hw > > > for > > > all PMCs based on the current vCPU state. This is needed because > > > Host-Only > > > and Guest-Only counters must be enabled/disabled at: > > > > > > - SVME changes: When EFER.SVME is modified, counters with Guest-Only bits > > > need their hardware enable state updated. > > > > > > - Nested transitions: When entering or leaving guest mode, Host-Only > > > counters should be disabled/enabled and Guest-Only counters should be > > > enabled/disabled accordingly. > > > > > > Introduce svm_enter_guest_mode() and svm_leave_guest_mode() wrappers that > > > call enter_guest_mode()/leave_guest_mode() followed by the PMU refresh, > > > ensuring the PMU state stays synchronized with guest mode transitions. > > > > > > Signed-off-by: Jim Mattson <[email protected]> > > > --- > > > arch/x86/kvm/svm/nested.c | 6 +++--- > > > arch/x86/kvm/svm/pmu.c | 12 ++++++++++++ > > > arch/x86/kvm/svm/svm.c | 2 ++ > > > arch/x86/kvm/svm/svm.h | 17 +++++++++++++++++ > > > 4 files changed, 34 insertions(+), 3 deletions(-) > > > > > > diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c > > > index de90b104a0dd..a7d1901f256b 100644 > > > --- a/arch/x86/kvm/svm/nested.c > > > +++ b/arch/x86/kvm/svm/nested.c > > > @@ -757,7 +757,7 @@ static void nested_vmcb02_prepare_control(struct > > > vcpu_svm *svm, > > > nested_svm_transition_tlb_flush(vcpu); > > > > > > /* Enter Guest-Mode */ > > > - enter_guest_mode(vcpu); > > > + svm_enter_guest_mode(vcpu); > > > > > > FWIW, I think this name is a bit confusing because we also have > > > enter_svm_guest_mode(). So we end up with: > > > > > > enter_svm_guest_mode() -> nested_vmcb02_prepare_control() -> > > > svm_enter_guest_mode() -> enter_guest_mode() > > > > > > I actually have another proposed change [1] that moves > > > enter_guest_mode() directly into enter_svm_guest_mode(), so the sequence > > > would end up being: > > > > > > enter_svm_guest_mode() -> svm_enter_guest_mode() -> enter_guest_mode() > > > > > Yes, that is confusing. What if I renamed the existing function to > > something like svm_nested_switch_to_vmcb02()? > > > > Alternatively, I could go back to introducing a new PMU_OP, call it > > from {enter,leave}_guest_mode(), and drop the wrappers. > > We could just call amd_pmu_refresh_host_guest_eventsel_hw() every time we > call enter_guest_mode() and leave_guest_mode(), which is more error-prone but > there's already other things in that category. > > We could also call it from svm_switch_vmcb(), which will add some calls to > extra places but I assume that would be fine? > > I personally prefer the former tbh, as it's otherwise easy to miss.
I'm not a fan of replicating code sequences. Maybe instead of a new PMU_OP, I could introduce a new KVM_X86_OP, which would be conceptually more general, even though the current usage would be the same. > > > > > > > > [1] > > > https://lore.kernel.org/kvm/[email protected]/ > > > > >
