The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From f4cfcd2d5aea4e96c5d483c476f3057b6b7baf6a Mon Sep 17 00:00:00 2001
From: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Date: Sat, 23 May 2020 19:14:55 +0300
Subject: [PATCH] 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@xxxxxxxxxxxxxxx
Fixes: 6e3ba4abce ("KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL")
Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
Message-Id: <20200523161455.3940-3-mlevitsk@xxxxxxxxxx>
Reviewed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c17e6eb9ad43..e0083a08da9e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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))
