Commit f4cfcd2d authored May 23, 2020 by Maxim Levitsky Committed by Paolo Bonzini May 27, 2020

KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally



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.

Cc: stable@vger.kernel.org
Fixes: 6e3ba4ab ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent 0abcc8f6

arch/x86/kvm/x86.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -5242,6 +5242,10 @@ static void kvm_init_msr_list(void)
		if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
		continue;
		break;
		case MSR_IA32_UMWAIT_CONTROL:
		if (!kvm_cpu_cap_has(X86_FEATURE_WAITPKG))
		continue;
		break;
		case MSR_IA32_RTIT_CTL:
		case MSR_IA32_RTIT_STATUS:
		if (!kvm_cpu_cap_has(X86_FEATURE_INTEL_PT))

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