On 18.08.20 23:15, Aaron Lewis wrote:
SDM volume 3: 24.6.9 "MSR-Bitmap Address" and APM volume 2: 15.11 "MS intercepts" describe MSR permission bitmaps. Permission bitmaps are used to control whether an execution of rdmsr or wrmsr will cause a vm exit. For userspace tracked MSRs it is required they cause a vm exit, so the host is able to forward the MSR to userspace. This change adds vmx/svm support to ensure the permission bitmap is properly set to cause a vm_exit to the host when rdmsr or wrmsr is used by one of the userspace tracked MSRs. Also, to avoid repeatedly setting them, kvm_make_request() is used to coalesce these into a single call. Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>
This is incomplete, as it doesn't cover all of the x2apic registers. There are also a few MSRs that IIRC are handled differently from this logic, such as EFER.
I'm really curious if this is worth the effort? I would be inclined to say that MSRs that KVM has direct access for need special handling one way or another.
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