[PATCH v2 43/54] KVM: x86/pmu: Update pmc_{read,write}_counter() to disconnect perf API

Mingwei Zhang
2024-05-06T05:31:49Z

Update pmc_{read,write}_counter() to disconnect perf API because
passthrough PMU does not use host PMU on backend. Because of that
pmc->counter contains directly the actual value of the guest VM when set by
the host (VMM) side.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
arch/x86/kvm/pmu.c | 5 +++++
arch/x86/kvm/pmu.h | 4 ++++
2 files changed, 9 insertions(+)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 06e70f74559d..12330d3f92f4 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -322,6 +322,11 @@ static void pmc_update_sample_period(struct kvm_pmc *pmc)

void pmc_write_counter(struct kvm_pmc *pmc, u64 val)
{
+ if (pmc_to_pmu(pmc)->passthrough) {
+ pmc->counter = val;
+ return;
+ }
+
/*
* Drop any unconsumed accumulated counts, the WRMSR is a write, not a
* read-modify-write. Adjust the counter value so that its value is
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 78a7f0c5f3ba..7e006cb61296 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -116,6 +116,10 @@ static inline u64 pmc_read_counter(struct kvm_pmc *pmc)
{
u64 counter, enabled, running;

+ counter = pmc->counter;
+ if (pmc_to_pmu(pmc)->passthrough)
+ return counter & pmc_bitmask(pmc);
+
counter = pmc->counter + pmc->emulated_counter;

if (pmc->perf_event && !pmc->is_paused)
--
2.45.0.rc1.225.g2a3ae87e7f-goog