Re: [Xen-devel] [PATCH] x86: optimize this_cpu()

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 13.07.10 at 16:45, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> wrote:
> On 13/07/2010 15:43, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
> 
>> I found it quite odd that, without any special comment to that
>> effect, I couldn't just add a single field to struct cpu_info without
>> causing breakage. The apparently odd extra padding field at
>> least provides a slight hint towards issues here. A similar issue
>> is that there is a silent requirement of "current_vcpu" being the
>> last field...
> 
> Where does that come from?

>From various assembly files, defining GET_CURRENT() or alike
on their own. grep-ing for STACK_SIZE had helped me noticing
the issue. Likewise GET_GUEST_REGS() implies that
"guest_cpu_user_regs" is the first field of struct cpu_info (but
this I would consider expected).

Jan


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