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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id n24sm7386923pgv.60.2021.08.27.10.23.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Aug 2021 10:23:09 -0700 (PDT) Date: Fri, 27 Aug 2021 17:23:05 +0000 From: Sean Christopherson To: Zhu Lingshan Cc: peterz@infradead.org, pbonzini@redhat.com, bp@alien8.de, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, kan.liang@linux.intel.com, ak@linux.intel.com, wei.w.wang@intel.com, eranian@google.com, liuxiangdong5@huawei.com, linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, like.xu.linux@gmail.com, boris.ostrvsky@oracle.com, Like Xu , Will Deacon , Marc Zyngier , Guo Ren , Nick Hu , Paul Walmsley , Boris Ostrovsky , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org, linux-riscv@lists.infradead.org, xen-devel@lists.xenproject.org Subject: Re: [PATCH V10 01/18] perf/core: Use static_call to optimize perf_guest_info_callbacks Message-ID: References: <20210806133802.3528-1-lingshan.zhu@intel.com> <20210806133802.3528-2-lingshan.zhu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210806133802.3528-2-lingshan.zhu@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-csky@vger.kernel.org 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; > }