Re: [Qemu-devel] [PATCH] target-i386: set model=6 on qemu64 & qemu32 CPU models

[Eduardo Habkost]

On Wed, Sep 11, 2013 at 11:53:46PM +0200, Andreas Färber wrote:
> Am 11.09.2013 10:37, schrieb Igor Mammedov:
> > On Wed, 11 Sep 2013 10:25:58 +0200
> > Andreas Färber <address@hidden> wrote:
> > 
> >> Am 11.09.2013 10:22, schrieb Igor Mammedov:
> >>> On Tue, 10 Sep 2013 17:48:59 -0300
> >>> Eduardo Habkost <address@hidden> wrote:
> >>>
> >>>> There's no Intel CPU with family=6,model=2, and Linux and Windows guests
> >>>> disable SEP when seeing that combination due to Pentium Pro erratum #82.
> >>>>
> >>>> In addition to just having SEP ignored by guests, Skype (and maybe other
> >>>> applications) runs sysenter directly without passing through ntdll on
> >>>> Windows, and crashes because Windows ignored the SEP CPUID bit.
> >>>>
> >>>> So, having model > 2 is a better default on qemu64 and qemu32 for two
> >>>> reasons: making SEP really available for guests, and avoiding crashing
> >>>> applications that work on bare metal.
> >>>>
> >>>> model=3 would fix the problem, but it causes CPU enumeration problems
> >>>> for Windows guests[1]. So this patch sets model=6, that matches "Athlon
> >>>> (PM core)" on AMD and "P2 with on-die L2 cache" on Intel and it allows
> >>>> Windows to use all CPUs as well as fixing sysenter.
> >>>>
> >>>> [1] https://bugzilla.redhat.com/show_bug.cgi?id=508623
> >>>>
> >>>> Cc: Andrea Arcangeli <address@hidden>
> >>>> Signed-off-by: Eduardo Habkost <address@hidden>
> >>>> ---
> >>>>  include/hw/i386/pc.h | 8 ++++++++
> >>>>  target-i386/cpu.c    | 4 ++--
> >>>>  2 files changed, 10 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> >>>> index 7fb04d8..195e962 100644
> >>>> --- a/include/hw/i386/pc.h
> >>>> +++ b/include/hw/i386/pc.h
> >>>> @@ -258,6 +258,14 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
> >>>>              .driver = TYPE_X86_CPU,\
> >>>>              .property = "pmu",\
> >>>>              .value = "on",\
> >>>> +        },{\
> >>>> +            .driver   = "qemu64-" TYPE_X86_CPU,\
> >>>> +            .property = "model",\
> >>>> +            .value    = stringify(2),\
> >>>> +        },{\
> >>>> +            .driver   = "qemu32-" TYPE_X86_CPU,\
> >>>> +            .property = "model",\
> >>>> +            .value    = stringify(3),\
> >>>>          }
> >>>>  
> >>>>  #define PC_COMPAT_1_4 \
> >>
> >> Shouldn't this hunk be in PC_COMPAT_1_6 rather than alongside PMU, which
> >> I believe was for 1_5?
> > grr, you are right.
> > my reviewed-by stands, provided compats are moved to PC_COMPAT_1_6.
> 
> Fixed now that Stefan's net-next pull has been merged. Thanks, applied
> to qom-cpu:
> https://github.com/afaerber/qemu-cpu/commits/qom-cpu

Thanks for catching and fixing it, and sorry for the confusion.

-- 
Eduardo