Messages in this thread | | | Subject | Re: [PATCH v2] x86/paravirt: Don't make vcpu_is_preempted() a callee-save function | From | Waiman Long <> | Date | Mon, 13 Feb 2017 14:42:18 -0500 |
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On 02/13/2017 05:53 AM, Peter Zijlstra wrote: > On Mon, Feb 13, 2017 at 11:47:16AM +0100, Peter Zijlstra wrote: >> That way we'd end up with something like: >> >> asm(" >> push %rdi; >> movslq %edi, %rdi; >> movq __per_cpu_offset(,%rdi,8), %rax; >> cmpb $0, %[offset](%rax); >> setne %al; >> pop %rdi; >> " : : [offset] "i" (((unsigned long)&steal_time) + offsetof(struct steal_time, preempted))); >> >> And if we could get rid of the sign extend on edi we could avoid all the >> push-pop nonsense, but I'm not sure I see how to do that (then again, >> this asm foo isn't my strongest point). > Maybe: > > movsql %edi, %rax; > movq __per_cpu_offset(,%rax,8), %rax; > cmpb $0, %[offset](%rax); > setne %al; > > ?
Yes, that looks good to me.
Cheers, Longman
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