On Mon, Aug 10, 2026 at 04:29:52PM +0800, Tina Zhang wrote: > Date: Mon, 10 Aug 2026 16:29:52 +0800 > From: Tina Zhang <[email protected]> > Subject: [PATCH v2 5/9] target/i386/kvm: Use AMD PMU MSR paths for Hygon > X-Mailer: git-send-email 2.43.7 > > On SVM, KVM uses the AMD PMU implementation and AMD PMU CPUID/MSR > layout. Hygon guests that enable PMU and request AMD PMU CPUID > features such as perfctr-core need QEMU's KVM PMU setup and MSR state > paths to use that layout too. > > The relevant QEMU KVM PMU paths are currently restricted to > AuthenticAMD guests: host/guest PMU compatibility checks, AMD PMU > information initialization, and AMD PMU MSR save/restore. For a Hygon > Dhyana guest with pmu=on, the compatibility check reports vPMU as > unsupported solely because the guest vendor is HygonGenuine rather than > AuthenticAMD. If the VM continues, QEMU still skips AMD PMU setup and > never saves or restores the AMD PMU MSRs for the Hygon guest. > > Treat Hygon as using the AMD PMU CPUID/MSR layout for these KVM PMU > paths. Because the PMU MSR layout is shared, accept both AMD and Hygon > hosts for guests using that layout. This intentionally allows the PMU > compatibility check to pass for AMD-host/Hygon-guest and > Hygon-host/AMD-guest combinations. > > This does not enable PMU, perfctr-core, or perfmon-v2 by default for the > Dhyana CPU model. On backward migration to older QEMU, Hygon PMU MSR > state may still be dropped because older QEMU did not write that state > back through the AMD PMU MSR KVM paths for Hygon guests. > > Signed-off-by: Tina Zhang <[email protected]> > --- > target/i386/kvm/kvm.c | 73 +++++++++++++++++++++++++++++++++---------- > 1 file changed, 56 insertions(+), 17 deletions(-)
The code looks good to me! It would be even better if this could be split into two patches - one dedicated to refactoring the vendor checks first, and another to add Hygon as a new AMD-compatible vendor. This would make it easier for maintainers to review, and the current commit message would more directly correspond to the Hygon-specific changes. :) Thanks, Zhao
