Re: [PATCH V10 01/18] perf/core: Use static_call to optimize perf_guest_info_callbacks
From: Sean Christopherson <seanjc@google.com>
Date: 2021-08-27 17:23:48
Also in:
kvmarm, linux-arm-kernel, linux-riscv, lkml, xen-devel
On Fri, Aug 06, 2021, Zhu Lingshan wrote:
quoted hunk ↗ jump to hunk
@@ -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; }