Re: [PULL 4/4] i386: Add "stibp" flag name

Eduardo Habkost
2018-12-12T17:11:51Z

On Wed, Dec 12, 2018 at 05:01:10PM +0000, Daniel P. Berrangé wrote:
> On Wed, Dec 12, 2018 at 04:57:42PM +0000, Lendacky, Thomas wrote:
> > On 12/11/2018 02:53 PM, Eduardo Habkost wrote:
> > > The STIBP flag may be supported by the host KVM module, so QEMU
> > > can allow it to be configured manually, and it can be exposed to
> > > guests when using "-cpu host".
> > >
> > > No additional migration code is required because the whole
> > > contents of spec_ctrl is already migrated in the "cpu/spec_ctrl"
> > > section.
> > >
> > > Corresponding KVM patch was submitted at:
> > > https://lore.kernel.org/lkml/20181205191956.31480-1-ehabkost@redhat.com/
> > >
> > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > Message-Id: <20181210180250.31299-1-ehabkost@redhat.com>
> > > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > > ---
> > > target/i386/cpu.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > index 86a934d450..12f559b6af 100644
> > > --- a/target/i386/cpu.c
> > > +++ b/target/i386/cpu.c
> > > @@ -1042,7 +1042,7 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
> > > NULL, NULL, NULL, NULL,
> > > NULL, NULL, "pconfig", NULL,
> > > NULL, NULL, NULL, NULL,
> > > - NULL, NULL, "spec-ctrl", NULL,
> > > + NULL, NULL, "spec-ctrl", "stibp",
> >
> > I guess I missed this earlier. Is there a corresponding patch for the AMD
> > STIBP bit (CPUID 0x80000008_EBX[15]) that is in KVM?
>
> This Intel STIBP patch is one that many distros have carried downstream
> since the flaw came to light.
>
> I've not seen any equiv patch for AMD STIBP bit, in either QMEU or libvirt,
> so guess that's a gap that needs filling.

I can submit a "amd-stibp" patch for completeness, although I
doubt many people will actually use the flag.

--
Eduardo