From 42501604363fa24d7b4dda33ff87feccf68058dd Mon Sep 17 00:00:00 2001 From: Maxim Levitsky Date: Wed, 11 Nov 2020 14:20:47 +0100 Subject: [PATCH] KVM: x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally [ Upstream commit f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a ] 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: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL") Signed-off-by: Maxim Levitsky Message-Id: <20200523161455.3940-3-mlevitsk@redhat.com> Reviewed-by: Sean Christopherson Signed-off-by: Paolo Bonzini (cherry picked from commit f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a use boot_cpu_has for checking the feature) Signed-off-by: Jack Wang Acked-by: Paolo Bonzini Signed-off-by: Sasha Levin --- 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 12e83297ea020..880a24889291c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5235,6 +5235,10 @@ static void kvm_init_msr_list(void) if (!kvm_x86_ops->rdtscp_supported()) continue; break; + case MSR_IA32_UMWAIT_CONTROL: + if (!boot_cpu_has(X86_FEATURE_WAITPKG)) + continue; + break; case MSR_IA32_RTIT_CTL: case MSR_IA32_RTIT_STATUS: if (!kvm_x86_ops->pt_supported())