On Wed, Jul 08, 2015 at 02:10:42PM +0200, Paolo Bonzini wrote:
>
>
> On 07/07/2015 19:21, Eduardo Habkost wrote:
> > On Tue, Jul 07, 2015 at 12:42:01PM +0200, Paolo Bonzini wrote:
> >> ABM is only implemented as a single instruction set by AMD; all AMD
> >> processors support both instructions or neither. Intel considers POPCNT
> >> as part of SSE4.2, and LZCNT as part of BMI1, but Intel also uses AMD's
> >> ABM flag to indicate support for both POPCNT and LZCNT. It has to be
> >> added to Haswell and Broadwell because Haswell, by adding LZCNT, has
> >> completed the ABM.
> >>
> >> Tested with "qemu-kvm -cpu Haswell-noTSX,enforce" (and also with older
> >> machine types) on an Haswell-EP machine.
> >>
> >> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> >> ---
> >> hw/i386/pc_piix.c | 4 ++++
> >> hw/i386/pc_q35.c | 4 ++++
> >> target-i386/cpu.c | 8 ++++----
> >> 3 files changed, 12 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> >> index 56cdcb9..d9e9987 100644
> >> --- a/hw/i386/pc_piix.c
> >> +++ b/hw/i386/pc_piix.c
> >> @@ -312,6 +312,10 @@ static void pc_compat_2_3(MachineState *machine)
> >> if (kvm_enabled()) {
> >> pcms->smm = ON_OFF_AUTO_OFF;
> >> }
> >> + x86_cpu_compat_set_features("Haswell", FEAT_8000_0001_ECX, 0,
> >> CPUID_EXT3_ABM);
> >> + x86_cpu_compat_set_features("Haswell-noTSX", FEAT_8000_0001_ECX, 0,
> >> CPUID_EXT3_ABM);
> >> + x86_cpu_compat_set_features("Broadwell", FEAT_8000_0001_ECX, 0,
> >> CPUID_EXT3_ABM);
> >> + x86_cpu_compat_set_features("Broadwell-noTSX", FEAT_8000_0001_ECX, 0,
> >> CPUID_EXT3_ABM);
> >
> > x86_cpu_compat_set_features() is not necessary anymore, please use
> > PC_COMPAT_2_3 to disable ABM.
>
> Would this be appropriate for 2.4, or should I just wait for 2.5?
As it can be easily worked around by using "-cpu <model>,+abm", I don't
think it qualifies as bug fix.
(Sorry, I just noticed you submitted the patch some time ago but it
slipped through the cracks).
--
Eduardo
