Re: [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function

From: Waiman Long
Date: Tue Feb 14 2017 - 09:47:37 EST

On 02/14/2017 04:39 AM, Peter Zijlstra wrote:
> On Mon, Feb 13, 2017 at 05:34:01PM -0500, Waiman Long wrote:
>> It is the address of &steal_time that will exceed the 32-bit limit.
> That seems extremely unlikely. That would mean we have more than 4G
> worth of per-cpu variables declared in the kernel.

I have some doubt about if the compiler is able to properly use
RIP-relative addressing for this. Anyway, it seems like constraints
aren't allowed for asm() when not in the function context, at least for
the the compiler that I am using (4.8.5). So it is a moot point.