Re: [PATCH v3 2/3] KVM: x86: Move pkru save/restore to x86.c

[Jim Mattson]

On Mon, May 11, 2020 at 4:33 PM Babu Moger <babu.moger@xxxxxxx> wrote:
>
> MPK feature is supported by both VMX and SVM. So we can
> safely move pkru state save/restore to common code. Also
> move all the pkru data structure to kvm_vcpu_arch.
>
> Also fixes the problem Jim Mattson pointed and suggested below.
>
> "Though rdpkru and wrpkru are contingent upon CR4.PKE, the PKRU
> resource isn't. It can be read with XSAVE and written with XRSTOR.
> So, if we don't set the guest PKRU value here(kvm_load_guest_xsave_state),
> the guest can read the host value.
>
> In case of kvm_load_host_xsave_state, guest with CR4.PKE clear could
> potentially use XRSTOR to change the host PKRU value"
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>

I would do the bugfix as a separate commit, to ease backporting it to
the stable branches.