Re: Core2 KVM trace 4.20 .. 5.0-rc4

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Zdenek Kaspar <zkaspar82@xxxxxxxxx> writes:

> Hi,
>
> old Core2 CPU: everything works well,
> but I see once in dmesg (5.0-rc4):
>
>
> unchecked MSR access error: RDMSR from 0x48b at rIP: 0xffffffffa0267570 
> (nested_vmx_setup_ctls_msrs+0xb0/0x210 [kvm_intel])

Oh,

0x48b is (MSR_IA32_VMX_PROCBASED_CTLS2) and SDM says we should only read
it "If ( CPUID.01H:ECX.[5] && IA32_VMX_PROCBASED_CTLS[63])". I'm
guessing that you're not using nested but now it is enabled by default.

so the following (completely untested) patch should work for you:

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 653830d0f3da..4bd0902bfd8c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5557,9 +5557,11 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps,
         * secondary cpu-based controls.  Do not include those that
         * depend on CPUID bits, they are added later by vmx_cpuid_update.
         */
-       rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
-               msrs->secondary_ctls_low,
-               msrs->secondary_ctls_high);
+       if (msrs->procbased_ctls_high & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)
+               rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
+                     msrs->secondary_ctls_low,
+                     msrs->secondary_ctls_high);
+
        msrs->secondary_ctls_low = 0;

Please let me now if this helps.

-- 
Vitaly