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Date: Tue, 26 May 2020 18:21:40 -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 2/2] kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally On Sat, May 23, 2020 at 07:14:55PM +0300, Maxim Levitsky wrote: > This msr is only available when the host supports WAITPKG feature. > > This breaks a nested guest, if the L1 hypervisor is set to ignore > unknown msrs, because the only other safety check that the > kernel does is that it attempts to read the msr and > rejects it if it gets an exception. > > Fixes: 6e3ba4abce KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL Same comments on the line wraps and Fixes tag. For the code: Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com> > Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com> > --- > arch/x86/kvm/x86.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index b226fb8abe41b..4752293312947 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5316,6 +5316,10 @@ static void kvm_init_msr_list(void) > min(INTEL_PMC_MAX_GENERIC, x86_pmu.num_counters_gp)) > continue; > break; > + case MSR_IA32_UMWAIT_CONTROL: > + if (!kvm_cpu_cap_has(X86_FEATURE_WAITPKG)) > + continue; > + break; > default: > break; > } > -- > 2.26.2 >
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