Messages in this thread | | | Date | Fri, 27 Aug 2021 17:23:05 +0000 | From | Sean Christopherson <> | Subject | Re: [PATCH V10 01/18] perf/core: Use static_call to optimize perf_guest_info_callbacks |
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On Fri, Aug 06, 2021, Zhu Lingshan wrote: > @@ -2944,18 +2966,21 @@ static unsigned long code_segment_base(struct pt_regs *regs) > > unsigned long perf_instruction_pointer(struct pt_regs *regs) > { > - if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) > - return perf_guest_cbs->get_guest_ip(); > + unsigned long ip = static_call(x86_guest_get_ip)(); > + > + if (likely(!ip))
Pivoting on ip==0 isn't correct, it's perfectly legal for a guest to execute from %rip=0. Unless there's some static_call() magic that supports this with a default function:
if (unlikely(!static_call(x86_guest_get_ip)(&ip))) regs->ip + code_segment_base(regs)
return ip;
The easiest thing is keep the existing:
if (unlikely(static_call(x86_guest_state)())) return static_call(x86_guest_get_ip)();
return regs->ip + code_segment_base(regs);
It's an extra call for PMIs in guest, but I don't think any of the KVM folks care _that_ much about the performance in this case.
> + ip = regs->ip + code_segment_base(regs); > > - return regs->ip + code_segment_base(regs); > + return ip; > }
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