On Wed, Mar 02, 2022 at 01:21:23PM +0100, Paolo Bonzini wrote:
> On 3/1/22 19:43, Oliver Upton wrote:
> > Right, a 1-setting of '{load,clear} IA32_BNDCFGS' should really be the
> > responsibility of userspace. My issue is that the commit message in
> > commit 5f76f6f5ff96 ("KVM: nVMX: Do not expose MPX VMX controls when
> > guest MPX disabled") suggests that userspace can expect these bits to be
> > configured based on guest CPUID. Furthermore, before commit aedbaf4f6afd
> > ("KVM: x86: Extract kvm_update_cpuid_runtime() from
> > kvm_update_cpuid()"), if userspace clears these bits, KVM will continue
> > to set them based on CPUID.
> >
> > What is the userspace expectation here? If we are saying that changes to
> > IA32_VMX_TRUE_{ENTRY,EXIT}_CTLS after userspace writes these MSRs is a
> > bug, then I agree aedbaf4f6afd is in fact a bugfix. But, the commit
> > message in 5f76f6f5ff96 seems to indicate that userspace wants KVM to
> > configure these bits based on guest CPUID.
>
> Yes, but I think it's reasonable that userspace wants to override them. It
> has to do that after KVM_SET_CPUID2, but that's okay too.
>
In that case, I can rework the tests at the end of this series to ensure
userspace's ability to override w/o a quirk. Sorry for the toil,
aedbaf4f6afd caused some breakage for us internally, but really is just
a userspace bug.
Is it possible to pick up patch 4/8 "KVM: x86: Introduce
KVM_CAP_DISABLE_QUIRKS2" independent of the rest of this series?
--
Thanks,
Oliver
