On Tue, 2020-05-26 at 18:13 -0700, Sean Christopherson wrote: > On Sat, May 23, 2020 at 07:14:53PM +0300, Maxim Levitsky wrote: > > On my AMD machine I noticed that I can't start any nested guests, > > because nested KVM (everything from master git branches) complains > > that it can't find msr MSR_IA32_UMWAIT_CONTROL which my system > > doesn't support > > at all anyway. > > > > I traced it to the recently added UMWAIT support to qemu and kvm. > > The kvm portion exposed the new MSR in KVM_GET_MSR_INDEX_LIST > > without > > checking that it the underlying feature is supported in CPUID. > > It happened to work when non nested because as a precation kvm, > > tries to read each MSR on host before adding it to that list, > > and when read gets a #GP it ignores it. > > > > When running nested, the L1 hypervisor can be set to ignore unknown > > msr read/writes (I need this for some other guests), thus this > > safety > > check doesn't work anymore. > > > > V2: * added a patch to setup correctly the X86_FEATURE_WAITPKG kvm > > capability > > * dropped the cosmetic fix patch as it is now fixed in kvm/queue > > > > Best regards, > > Maxim Levitsky > > > > Maxim Levitsky (2): > > kvm/x86/vmx: enable X86_FEATURE_WAITPKG in KVM capabilities > > kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally > > Standard scoping in the shortlog is "KVM: VMX:" and "KVM: x86:". Noted and I will use it from now on. Thanks! Best regards, Maxim Levitsky > > > arch/x86/kvm/vmx/vmx.c | 3 +++ > > arch/x86/kvm/x86.c | 4 ++++ > > 2 files changed, 7 insertions(+) > > > > -- > > 2.26.2 > > > >
