On Fri, Mar 3, 2023 at 2:23 PM Aaron Lewis <aaronlewis@xxxxxxxxxx> wrote:
>
> On Fri, Mar 3, 2023 at 9:23 PM Mingwei Zhang <mizhang@xxxxxxxxxx> wrote:
> >
> > On Fri, Feb 24, 2023, Aaron Lewis wrote:
> > > Be a good citizen and don't allow any of the supported MPX xfeatures[1]
> > > to be set if they can't all be set. That way userspace or a guest
> > > doesn't fail if it attempts to set them in XCR0.
> > >
> > > [1] CPUID.(EAX=0DH,ECX=0):EAX.BNDREGS[bit-3]
> > > CPUID.(EAX=0DH,ECX=0):EAX.BNDCSR[bit-4]
> > >
> > > Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
> > > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
Reviewed-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
> > > ---
> > > arch/x86/kvm/cpuid.c | 15 ++++++++++++++-
> > > 1 file changed, 14 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > > index e1165c196970..b2e7407cd114 100644
> > > --- a/arch/x86/kvm/cpuid.c
> > > +++ b/arch/x86/kvm/cpuid.c
> > > @@ -60,9 +60,22 @@ u32 xstate_required_size(u64 xstate_bv, bool compacted)
> > > return ret;
> > > }
> > >
> > > +static u64 sanitize_xcr0(u64 xcr0)
> > > +{
> > > + u64 mask;
> > > +
> > > + mask = XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR;
> > > + if ((xcr0 & mask) != mask)
> > > + xcr0 &= ~mask;
> > > +
> > > + return xcr0;
> > > +}
> >
> > Is it better to put sanitize_xcr0() into the previous patch? If we do
> > that, this one will be just adding purely the MPX related logic and thus
> > cleaner I think.
>
> I don't mind doing that. I considered putting in its own commit
> actually. The only reason I didn't is I wasn't sure it was
> appropriate to have a commit that only added an empty function. If
> that's okay I think I'd lean more towards doing it that way.
>
Yeah, either way works for me.
