[PATCH v1 1/3] RISC-V: KVM: Preserve firmware counter value across stop/start

[SeungJu Cheon]

Firmware events accumulate in kvpmu->fw_event[].value while running,
but counter stop only clears fw_event[].started without saving the
value back to pmc->counter_val. A subsequent counter start without
SBI_PMU_START_FLAG_SET_INIT_VALUE reloads the stale counter_val into
fw_event[].value, losing all events counted so far.

Save fw_event[].value into counter_val when actually stopping a
running counter, and remove the now redundant synchronization from
the snapshot path.

Fixes: badc386869e2c ("RISC-V: KVM: Support firmware events")
Signed-off-by: SeungJu Cheon <suunj1331 at gmail.com>
---
 arch/riscv/kvm/vcpu_pmu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 2025b664961c..56dd5b1b2846 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -671,10 +671,12 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
 				goto out;
 			}
 
-			if (!kvpmu->fw_event[fevent_code].started)
+			if (!kvpmu->fw_event[fevent_code].started) {
 				sbiret = SBI_ERR_ALREADY_STOPPED;
-
-			kvpmu->fw_event[fevent_code].started = false;
+			} else {
+				kvpmu->fw_event[fevent_code].started = false;
+				pmc->counter_val = kvpmu->fw_event[fevent_code].value;
+			}
 		} else if (pmc->perf_event) {
 			if (pmc->started) {
 				/* Stop counting the counter */
@@ -692,9 +694,7 @@ int kvm_riscv_vcpu_pmu_ctr_stop(struct kvm_vcpu *vcpu, unsigned long ctr_base,
 		}
 
 		if (snap_flag_set && !sbiret) {
-			if (pmc->cinfo.type == SBI_PMU_CTR_TYPE_FW)
-				pmc->counter_val = kvpmu->fw_event[fevent_code].value;
-			else if (pmc->perf_event)
+			if (pmc->perf_event)
 				pmc->counter_val += perf_event_read_value(pmc->perf_event,
 									  &enabled, &running);
 			/*
-- 
2.52.0