Re: [Xen-devel] [PATCH 2/2] x86/cpu: Improvements to get_cpu_vendor()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 03/01/17 12:40, Jan Beulich wrote:
>>>> On 03.01.17 at 13:06, <andrew.cooper3@xxxxxxxxxx> wrote:
>> Comparing 3 integers is more efficient than using strcmp(), and is more 
>> useful
>> to the gcv_guest case than having to fabricate a suitable string to pass.  
>> The
>> gcv_host cases have both options easily to hand, and experimentally, the
>> resulting code is more efficient.
>>
>> While modifying get_cpu_vendor(), fix a bug where this_cpu got updated even 
>> in
>> the gcv_guest case.
> Isn't this something we'd better fix separately, to ease backporting?

I can do.

>
>> Update the cpu_dev structure to be more efficient.  c_vendor[] only needs to
>> be 8 bytes long to cover all the CPU drivers Xen has, which avoids storing an
>> 8-byte pointer to 8 bytes of data.  Drop c_ident[1] as we have no CPU drivers
>> with a second ident string, and turn it into a transparent union to allow
>> access to the integer values directly.
> I think "transparent" is misleading here, as you don't add the respective
> gcc attribute. I think you mean "unnamed".

Yes sorry.  My mistake.

>
>> This avoids all need for the vendor_id union in update_domain_cpuid_info().
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> For the patch itself
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Does this still stand if I split the patch into two, for easier backport?

~Andrew

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