[RFC 7/9] RISC-V: KVM: Implement trap & emulate for hpmcounters

Atish Patra
2022-07-18T17:06:18Z

As the KVM guests only see the virtual PMU counters, all hpmcounter
access should trap and KVM emulates the read access on behalf of guests.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
arch/riscv/include/asm/kvm_vcpu_pmu.h | 16 +++++++++
arch/riscv/kvm/vcpu_insn.c | 1 +
arch/riscv/kvm/vcpu_pmu.c | 47 +++++++++++++++++++++++----
3 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h
index bffee052f2ae..5410236b62a8 100644
--- a/arch/riscv/include/asm/kvm_vcpu_pmu.h
+++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h
@@ -39,6 +39,19 @@ struct kvm_pmu {
#define pmu_to_vcpu(pmu) (container_of((pmu), struct kvm_vcpu, arch.pmu))
#define pmc_to_pmu(pmc) (&(pmc)->vcpu->arch.pmu)

+#if defined(CONFIG_32BIT)
+#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
+{ .base = CSR_CYCLEH, .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm }, \
+{ .base = CSR_CYCLE, .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm },
+#else
+#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
+{ .base = CSR_CYCLE, .count = 31, .func = kvm_riscv_vcpu_pmu_read_hpm },
+#endif
+
+int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
+ unsigned long *val, unsigned long new_val,
+ unsigned long wr_mask);
+
int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, unsigned long *out_val);
int kvm_riscv_vcpu_pmu_ctr_info(struct kvm_vcpu *vcpu, unsigned long cidx,
unsigned long *ctr_info);
@@ -59,6 +72,9 @@ void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu);
#else
struct kvm_pmu {
};
+#define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \
+{ .base = 0, .count = 0, .func = NULL },
+

static inline int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
{
diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
index 0aa334f853c8..7c2a4b1a69f7 100644
--- a/arch/riscv/kvm/vcpu_insn.c
+++ b/arch/riscv/kvm/vcpu_insn.c
@@ -215,6 +215,7 @@ struct csr_func {
};

static const struct csr_func csr_funcs[] = {
+ KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS
};

/**
diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c
index 3168ed740bdd..5434051f495d 100644
--- a/arch/riscv/kvm/vcpu_pmu.c
+++ b/arch/riscv/kvm/vcpu_pmu.c
@@ -14,6 +14,46 @@
#include <asm/kvm_vcpu_pmu.h>
#include <linux/kvm_host.h>

+int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
+ unsigned long *out_val)
+{
+ struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
+ struct kvm_pmc *pmc;
+ u64 enabled, running;
+
+ if (!kvpmu)
+ return -EINVAL;
+
+ pmc = &kvpmu->pmc[cidx];
+ if (!pmc->perf_event)
+ return -EINVAL;
+
+ pmc->counter_val += perf_event_read_value(pmc->perf_event, &enabled, &running);
+ *out_val = pmc->counter_val;
+
+ return 0;
+}
+
+int kvm_riscv_vcpu_pmu_read_hpm(struct kvm_vcpu *vcpu, unsigned int csr_num,
+ unsigned long *val, unsigned long new_val,
+ unsigned long wr_mask)
+{
+ struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
+ int cidx, ret = KVM_INSN_CONTINUE_NEXT_SEPC;
+
+ if (!kvpmu)
+ return KVM_INSN_EXIT_TO_USER_SPACE;
+ //TODO: Should we check if vcpu pmu is initialized or not!
+ if (wr_mask)
+ return KVM_INSN_ILLEGAL_TRAP;
+ cidx = csr_num - CSR_CYCLE;
+
+ if (kvm_riscv_vcpu_pmu_ctr_read(vcpu, cidx, val) < 0)
+ return KVM_INSN_EXIT_TO_USER_SPACE;
+
+ return ret;
+}
+
int kvm_riscv_vcpu_pmu_num_ctrs(struct kvm_vcpu *vcpu, unsigned long *out_val)
{
struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
@@ -60,13 +100,6 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
return 0;
}

-int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
- unsigned long *out_val)
-{
- /* TODO */
- return 0;
-}
-
int kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu)
{
int i = 0, num_hw_ctrs, num_fw_ctrs, hpm_width;
--
2.25.1