Re: [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE_RDTSCP control is unsupported

From: Jim Mattson
Date: Tue May 04 2021 - 13:37:44 EST

On Tue, May 4, 2021 at 10:17 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> Clear KVM's RDPID capability if the ENABLE_RDTSCP secondary exec control is
> unsupported. Despite being enumerated in a separate CPUID flag, RDPID is
> bundled under the same VMCS control as RDTSCP and will #UD in VMX non-root
> if ENABLE_RDTSCP is not enabled.
> Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

But KVM will happily emulate RDPID if the instruction causes a #UD
VM-exit, won't it? See commit fb6d4d340e05 (KVM: x86: emulate RDPID).