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Date: Tue, 26 May 2020 18:13:44 -0700 From: Sean Christopherson <sean.j.christopherson@...el.com> To: Maxim Levitsky <mlevitsk@...hat.com> Cc: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Tao Xu <tao3.xu@...el.com>, Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, Wanpeng Li <wanpengli@...cent.com>, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, Vitaly Kuznetsov <vkuznets@...hat.com>, Jingqi Liu <jingqi.liu@...el.com> Subject: Re: [PATCH 0/2] Fix issue with not starting nesting guests on my system 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:". > > arch/x86/kvm/vmx/vmx.c | 3 +++ > arch/x86/kvm/x86.c | 4 ++++ > 2 files changed, 7 insertions(+) > > -- > 2.26.2 > >
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