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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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?

> 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".

> 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>

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel