Re: [Qemu-devel] [PATCH rebased for-2.4] target-i386: add ABM to Haswell* and Broadwell* CPU models

[Paolo Bonzini <pbonzini@redhat.com>]

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 <pbonzini@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?

Paolo