Re: [Qemu-devel] [PATCH] i386: Disable TOPOEXT by default on "-cpu host"

[Moger, Babu]

Looks good. Did some basic testing.

Reviewed-by: Babu Moger <address@hidden>

> -----Original Message-----
> From: Richard W.M. Jones <address@hidden>
> Sent: Friday, August 10, 2018 2:41 AM
> To: Eduardo Habkost <address@hidden>
> Cc: address@hidden; Paolo Bonzini <address@hidden>;
> Richard Henderson <address@hidden>; Moger, Babu
> <address@hidden>
> Subject: Re: [PATCH] i386: Disable TOPOEXT by default on "-cpu host"
> 
> On Thu, Aug 09, 2018 at 07:18:52PM -0300, Eduardo Habkost wrote:
> > Enabling TOPOEXT is always allowed, but it can't be enabled
> > blindly by "-cpu host" because it may make guests crash if the
> > rest of the cache topology information isn't provided or isn't
> > consistent.
> >
> > This addresses the bug reported at:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1613277
> >
> > Signed-off-by: Eduardo Habkost <address@hidden>
> > ---
> >  target/i386/cpu.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 723e02221e..3ac627978f 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -849,6 +849,12 @@ static FeatureWordInfo
> feature_word_info[FEATURE_WORDS] = {
> >          },
> >          .cpuid_eax = 0x80000001, .cpuid_reg = R_ECX,
> >          .tcg_features = TCG_EXT3_FEATURES,
> > +        /*
> > +         * TOPOEXT is always allowed but can't be enabled blindly by
> > +         * "-cpu host", as it requires consistent cache topology info
> > +         * to be provided so it doesn't confuse guests.
> > +         */
> > +        .no_autoenable_flags = CPUID_EXT3_TOPOEXT,
> >      },
> >      [FEAT_C000_0001_EDX] = {
> >          .feat_names = {
> 
> Can confirm that this fixes the problem observed on the original AMD
> Phenom machine, using qemu from git (@6ad908053) + your patch.
> Therefore:
> 
> Tested-by: Richard W.M. Jones <address@hidden>
> 
> Thanks,
> 
> Rich.
> 
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
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