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MIME-Version: 1.0 Message-Id: <20240626-smcntrpmf_v7-v7-10-bb0f10af7fa9@rivosinc.com> References: <20240626-smcntrpmf_v7-v7-0-bb0f10af7fa9@rivosinc.com> In-Reply-To: <20240626-smcntrpmf_v7-v7-0-bb0f10af7fa9@rivosinc.com> To: qemu-riscv@nongnu.org, qemu-devel@nongnu.org Cc: Rajnesh Kanwal , Atish Patra , palmer@dabbelt.com, liwei1518@gmail.com, zhiwei_liu@linux.alibaba.com, bin.meng@windriver.com, dbarboza@ventanamicro.com, alistair.francis@wdc.com X-Mailer: b4 0.15-dev-13183 Received-SPF: pass client-ip=2607:f8b0:4864:20::633; envelope-from=atishp@rivosinc.com; helo=mail-pl1-x633.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Rajnesh Kanwal In case of programmable counters configured to count inst/cycles we often end-up with counter not incrementing at all from kernel's perspective. For example: - Kernel configures hpm3 to count instructions and sets hpmcounter to -10000 and all modes except U mode are inhibited. - In QEMU we configure a timer to expire after ~10000 instructions. - Problem is, it's often the case that kernel might not even schedule Umode task and we hit the timer callback in QEMU. - In the timer callback we inject the interrupt into kernel, kernel runs the handler and reads hpmcounter3 value. - Given QEMU maintains individual counters to count for each privilege mode, and given umode never ran, the umode counter didn't increment and QEMU returns same value as was programmed by the kernel when starting the counter. - Kernel checks for overflow using previous and current value of the counter and reprograms the counter given there wasn't an overflow as per the counter value. (Which itself is a problem. We have QEMU telling kernel that counter3 overflowed but the counter value returned by QEMU doesn't seem to reflect that.). This change makes sure that timer is reprogrammed from the handler if the counter didn't overflow based on the counter value. Second, this change makes sure that whenever the counter is read, it's value is updated to reflect the latest count. Signed-off-by: Rajnesh Kanwal Reviewed-by: Daniel Henrique Barboza --- target/riscv/csr.c | 5 ++++- target/riscv/pmu.c | 30 +++++++++++++++++++++++++++--- target/riscv/pmu.h | 2 ++ 3 files changed, 33 insertions(+), 4 deletions(-) diff --git a/target/riscv/csr.c b/target/riscv/csr.c index 150e02f080ec..91172b90e000 100644 --- a/target/riscv/csr.c +++ b/target/riscv/csr.c @@ -970,6 +970,9 @@ static target_ulong riscv_pmu_ctr_get_fixed_counters_val(CPURISCVState *env, goto done; } + /* Update counter before reading. */ + riscv_pmu_update_fixed_ctrs(env, env->priv, env->virt_enabled); + if (!(cfg_val & MCYCLECFG_BIT_MINH)) { curr_val += counter_arr[PRV_M]; } @@ -1053,7 +1056,7 @@ static RISCVException write_mhpmcounterh(CPURISCVState *env, int csrno, return RISCV_EXCP_NONE; } -static RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val, +RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val, bool upper_half, uint32_t ctr_idx) { PMUCTRState *counter = &env->pmu_ctrs[ctr_idx]; diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c index 63420d9f3679..a4729f6c53bb 100644 --- a/target/riscv/pmu.c +++ b/target/riscv/pmu.c @@ -425,6 +425,8 @@ static void pmu_timer_trigger_irq(RISCVCPU *cpu, target_ulong *mhpmevent_val; uint64_t of_bit_mask; int64_t irq_trigger_at; + uint64_t curr_ctr_val, curr_ctrh_val; + uint64_t ctr_val; if (evt_idx != RISCV_PMU_EVENT_HW_CPU_CYCLES && evt_idx != RISCV_PMU_EVENT_HW_INSTRUCTIONS) { @@ -454,6 +456,26 @@ static void pmu_timer_trigger_irq(RISCVCPU *cpu, return; } + riscv_pmu_read_ctr(env, (target_ulong *)&curr_ctr_val, false, ctr_idx); + ctr_val = counter->mhpmcounter_val; + if (riscv_cpu_mxl(env) == MXL_RV32) { + riscv_pmu_read_ctr(env, (target_ulong *)&curr_ctrh_val, true, ctr_idx); + curr_ctr_val = curr_ctr_val | (curr_ctrh_val << 32); + ctr_val = ctr_val | + ((uint64_t)counter->mhpmcounterh_val << 32); + } + + /* + * We can not accommodate for inhibited modes when setting up timer. Check + * if the counter has actually overflowed or not by comparing current + * counter value (accommodated for inhibited modes) with software written + * counter value. + */ + if (curr_ctr_val >= ctr_val) { + riscv_pmu_setup_timer(env, curr_ctr_val, ctr_idx); + return; + } + if (cpu->pmu_avail_ctrs & BIT(ctr_idx)) { /* Generate interrupt only if OF bit is clear */ if (!(*mhpmevent_val & of_bit_mask)) { @@ -475,7 +497,7 @@ void riscv_pmu_timer_cb(void *priv) int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value, uint32_t ctr_idx) { - uint64_t overflow_delta, overflow_at; + uint64_t overflow_delta, overflow_at, curr_ns; int64_t overflow_ns, overflow_left = 0; RISCVCPU *cpu = env_archcpu(env); PMUCTRState *counter = &env->pmu_ctrs[ctr_idx]; @@ -506,8 +528,10 @@ int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value, uint32_t ctr_idx) } else { return -1; } - overflow_at = (uint64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + - overflow_ns; + curr_ns = (uint64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL); + overflow_at = curr_ns + overflow_ns; + if (overflow_at <= curr_ns) + overflow_at = UINT64_MAX; if (overflow_at > INT64_MAX) { overflow_left += overflow_at - INT64_MAX; diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h index ca40cfeed647..3853d0e2629e 100644 --- a/target/riscv/pmu.h +++ b/target/riscv/pmu.h @@ -36,5 +36,7 @@ int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t value, uint32_t ctr_idx); void riscv_pmu_update_fixed_ctrs(CPURISCVState *env, target_ulong newpriv, bool new_virt); +RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val, + bool upper_half, uint32_t ctr_idx); #endif /* RISCV_PMU_H */