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06 Nov 2024 12:38:30 -0800 Received: from [10.212.82.230] (kliang2-mobl1.ccr.corp.intel.com [10.212.82.230]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by linux.intel.com (Postfix) with ESMTPS id 2880520B5703; Wed, 6 Nov 2024 12:38:26 -0800 (PST) Message-ID: <89b46b99-e9fc-4ce4-84b2-b24f565db8d5@linux.intel.com> Date: Wed, 6 Nov 2024 15:38:25 -0500 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 5/5] perf: Correct perf sampling with guest VMs To: Oliver Upton Cc: Colton Lewis , kvm@vger.kernel.org, Sean Christopherson , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , Will Deacon , Russell King , Catalin Marinas , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org References: <20241105195603.2317483-1-coltonlewis@google.com> <20241105195603.2317483-6-coltonlewis@google.com> <007cfed1-111d-45aa-b873-24cca9d4af01@linux.intel.com> Content-Language: en-US From: "Liang, Kan" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024-11-06 2:53 p.m., Oliver Upton wrote: > On Wed, Nov 06, 2024 at 11:07:53AM -0500, Liang, Kan wrote: >>> +#ifndef perf_arch_guest_misc_flags >>> +static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) >>> +{ >>> + unsigned long guest_state = perf_guest_state(); >>> + >>> + if (guest_state & PERF_GUEST_USER) >>> + return PERF_RECORD_MISC_GUEST_USER; >>> + >>> + if (guest_state & PERF_GUEST_ACTIVE) >>> + return PERF_RECORD_MISC_GUEST_KERNEL; >> >> Is there by any chance to add a PERF_GUEST_KERNEL flag in KVM? > > Why do we need another flag? As it stands today, the vCPU is either in > user mode or kernel mode. > >> The PERF_GUEST_ACTIVE flag check looks really confusing. > > Perhaps instead: > > static inline unsigned long perf_arch_guest_misc_flags(struct pt_regs *regs) > { > unsigned long guest_state = perf_guest_state(); > > if (!(guest_state & PERF_GUEST_ACTIVE)) > return 0; > > return (guest_state & PERF_GUEST_USER) ? PERF_RECORD_MISC_GUEST_USER : > PERF_RECORD_MISC_GUEST_KERNEL; > } Yes, this one is much clear. Can a similar change be done for the x86 perf_arch_guest_misc_flags() in the previous patch? Thanks, Kan