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[82.26.13.58]) by smtp.gmail.com with ESMTPSA id n16-20020a1c7210000000b003fe1630a8f0sm1502871wmc.24.2023.08.02.04.59.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Aug 2023 04:59:32 -0700 (PDT) From: Rajnesh Kanwal To: anshuman.khandual@arm.com Cc: acme@kernel.org, broonie@kernel.org, catalin.marinas@arm.com, james.clark@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mark.rutland@arm.com, maz@kernel.org, mingo@redhat.com, peterz@infradead.org, robh@kernel.org, suzuki.poulose@arm.com, will@kernel.org, atishp@rivosinc.com Subject: Re: [PATCH V13 - RESEND 09/10] arm64/perf: Implement branch records save on task sched out Date: Wed, 2 Aug 2023 12:59:31 +0100 Message-Id: <20230802115931.12212-1-rkanwal@rivosinc.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230711082455.215983-10-anshuman.khandual@arm.com> References: <20230711082455.215983-10-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org >diff --git a/drivers/perf/arm_brbe.c b/drivers/perf/arm_brbe.c >index 203cd4f350d5..2177632befa6 100644 >--- a/drivers/perf/arm_brbe.c >+++ b/drivers/perf/arm_brbe.c >@@ -165,6 +165,36 @@ static int stitch_stored_live_entries(struct brbe_regset *stored, > return min(nr_live + nr_stored, nr_max); > } > >+static int brbe_branch_save(struct brbe_regset *live, int nr_hw_entries) >+{ >+ u64 brbfcr = read_sysreg_s(SYS_BRBFCR_EL1); >+ int nr_live; >+ >+ write_sysreg_s(brbfcr | BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1); >+ isb(); >+ >+ nr_live = capture_brbe_regset(live, nr_hw_entries); >+ >+ write_sysreg_s(brbfcr & ~BRBFCR_EL1_PAUSED, SYS_BRBFCR_EL1); >+ isb(); >+ >+ return nr_live; >+} >+ >+void armv8pmu_branch_save(struct arm_pmu *arm_pmu, void *ctx) >+{ >+ struct arm64_perf_task_context *task_ctx = ctx; >+ struct brbe_regset live[BRBE_MAX_ENTRIES]; >+ int nr_live, nr_store, nr_hw_entries; >+ >+ nr_hw_entries = brbe_get_numrec(arm_pmu->reg_brbidr); >+ nr_live = brbe_branch_save(live, nr_hw_entries); >+ nr_store = task_ctx->nr_brbe_records; >+ nr_store = stitch_stored_live_entries(task_ctx->store, live, nr_store, >+ nr_live, nr_hw_entries); >+ task_ctx->nr_brbe_records = nr_store; >+} Asking out-of-curiosity. Have you thought about virtualization use case. Current LBR implementation create an event for the guest and save/restore happens using the sched_task callback. (Correct me if I am wrong). Given you are only saving and processing those saved entries, how do you plan to expose the entries to the guest? Thanks Rajnesh >+ > /* > * Generic perf branch filters supported on BRBE > * >diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c >index 408974d5c57b..aa3c7b3dcdd6 100644 >--- a/drivers/perf/arm_pmuv3.c >+++ b/drivers/perf/arm_pmuv3.c >@@ -923,9 +923,19 @@ static int armv8pmu_user_event_idx(struct perf_event *event) > static void armv8pmu_sched_task(struct perf_event_pmu_context *pmu_ctx, bool sched_in) > { > struct arm_pmu *armpmu = to_arm_pmu(pmu_ctx->pmu); >+ void *task_ctx = pmu_ctx ? pmu_ctx->task_ctx_data : NULL; > >- if (sched_in && armpmu->has_branch_stack) >- armv8pmu_branch_reset(); >+ if (armpmu->has_branch_stack) { >+ /* Save branch records in task_ctx on sched out */ >+ if (task_ctx && !sched_in) { >+ armv8pmu_branch_save(armpmu, task_ctx); >+ return; >+ } >+ >+ /* Reset branch records on sched in */ >+ if (sched_in) >+ armv8pmu_branch_reset(); >+ } > }