Re: [Xen-devel] [PATCH v3 1/9] x86: define CPUINFO_features used as the base offset for cpu features

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.04.14 at 10:55, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 28/04/14 04:13, Feng Wu wrote:
>> This patch defines CPUINFO_features which can be used as the base of
>> the offset for cpu features.
>>
>> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
>> ---
>>  xen/arch/x86/boot/head.S          | 2 +-
>>  xen/arch/x86/x86_64/asm-offsets.c | 2 +-
>>  xen/include/asm-x86/asm_defns.h   | 2 ++
>>  3 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
>> index 1777c17..2b5b26a 100644
>> --- a/xen/arch/x86/boot/head.S
>> +++ b/xen/arch/x86/boot/head.S
>> @@ -131,7 +131,7 @@ __start:
>>          mov     $0x80000001,%eax
>>          cpuid
>>  1:      mov     %edx,sym_phys(cpuid_ext_features)
>> -        mov     %edx,sym_phys(boot_cpu_data)+CPUINFO86_ext_features
>> +        mov     %edx,sym_phys(boot_cpu_data)+CPUINFO_ext_features
> 
> Personally I feel this would be better as CPUINFO_features + 4, rather
> than having another #define in asm_defn.h solely for this purpose.

It should indeed be done here, without the extra #define, but also
without the literal 4. Our main goal here is to collect the LM bit, so
just calculate the number from X86_FEATURE_LM.

Jan


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