Messages in this thread | | | Subject | Re: [PATCH 0/2] Fix issue with not starting nesting guests on my system | From | Krish Sadhukhan <> | Date | Tue, 26 May 2020 18:03:32 -0700 |
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On 5/23/20 9:14 AM, 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 > > arch/x86/kvm/vmx/vmx.c | 3 +++ > arch/x86/kvm/x86.c | 4 ++++ > 2 files changed, 7 insertions(+) > Nit: The added 'break' statement in patch# 2 is not required.
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
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