Re: [PATCH v4 2/2] x86/kvm: Provide optimized version of vcpu_is_preempted() for x86-64
From: Waiman Long
Date: Thu Feb 16 2017 - 16:00:27 EST
On 02/16/2017 11:48 AM, Peter Zijlstra wrote:
> On Wed, Feb 15, 2017 at 04:37:50PM -0500, Waiman Long wrote:
>> + * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and
>> + * restoring to/from the stack. It is assumed that the preempted value
>> + * is at an offset of 16 from the beginning of the kvm_steal_time structure
>> + * which is verified by the BUILD_BUG_ON() macro below.
>> + */
>> +#define PREEMPTED_OFFSET 16
> As per Andrew's suggestion, the 'right' way is something like so.
Thanks for the tip. I was not aware of the asm-offsets stuff. I will
update the patch to use it.