Re: [PATCH v4 10/15] RISC-V: KVM: Support 64 bit firmware counters on RV32

On Wed, Feb 28, 2024 at 05:01:25PM -0800, Atish Patra wrote:

The SBI v2.0 introduced a fw_read_hi function to read 64 bit firmware counters for RV32 based systems.

Add infrastructure to support that.

Reviewed-by: Anup Patel anup@brainfault.org Signed-off-by: Atish Patra atishp@rivosinc.com

---

arch/riscv/include/asm/kvm_vcpu_pmu.h | 4 ++- arch/riscv/kvm/vcpu_pmu.c | 37 ++++++++++++++++++++++++++- arch/riscv/kvm/vcpu_sbi_pmu.c | 6 +++++ 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h index 8cb21a4f862c..e0ad27dea46c 100644 --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h @@ -20,7 +20,7 @@ static_assert(RISCV_KVM_MAX_COUNTERS <= 64); struct kvm_fw_event { /* Current value of the event */

• unsigned long value;

• u64 value;

/* Event monitoring status */ bool started; @@ -91,6 +91,8 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba struct kvm_vcpu_sbi_return *retdata); int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx, struct kvm_vcpu_sbi_return *retdata); +int kvm_riscv_vcpu_pmu_fw_ctr_read_hi(struct kvm_vcpu *vcpu, unsigned long cidx,

• 		      struct kvm_vcpu_sbi_return *retdata);
  

void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu); int kvm_riscv_vcpu_pmu_setup_snapshot(struct kvm_vcpu *vcpu, unsigned long saddr_low, unsigned long saddr_high, unsigned long flags, diff --git a/arch/riscv/kvm/vcpu_pmu.c b/arch/riscv/kvm/vcpu_pmu.c index a02f7b981005..469bb430cf97 100644 --- a/arch/riscv/kvm/vcpu_pmu.c +++ b/arch/riscv/kvm/vcpu_pmu.c @@ -196,6 +196,29 @@ static int pmu_get_pmc_index(struct kvm_pmu *pmu, unsigned long eidx, return kvm_pmu_get_programmable_pmc_index(pmu, eidx, cbase, cmask); } +static int pmu_fw_ctr_read_hi(struct kvm_vcpu *vcpu, unsigned long cidx,

• 	      unsigned long *out_val)
  

+{

• struct kvm_pmu *kvpmu = vcpu_to_pmu(vcpu);
• struct kvm_pmc *pmc;
• int fevent_code;
• if (!IS_ENABLED(CONFIG_32BIT))

Let's remove the CONFIG_32BIT check in kvm_sbi_ext_pmu_handler() and then set *out_val to zero here and return success. Either that, or we should WARN or something here since it's a KVM bug to get here with !CONFIG_32BIT.

• return -EINVAL;
  

• pmc = &kvpmu->pmc[cidx];

Uh oh! We're missing range validation of cidx! And I see we're missing it in pmu_ctr_read() too. We need the same check we have in kvm_riscv_vcpu_pmu_ctr_info(). I think the other SBI functions are OK, but it's worth a triple check.

• if (pmc->cinfo.type != SBI_PMU_CTR_TYPE_FW)

• return -EINVAL;
  

• fevent_code = get_event_code(pmc->event_idx);
• pmc->counter_val = kvpmu->fw_event[fevent_code].value;
• *out_val = pmc->counter_val >> 32;
• return 0;

+}

static int pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx, unsigned long *out_val) { @@ -702,6 +725,18 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba return 0; } +int kvm_riscv_vcpu_pmu_fw_ctr_read_hi(struct kvm_vcpu *vcpu, unsigned long cidx,

• 		      struct kvm_vcpu_sbi_return *retdata)
  

+{

• int ret;
• ret = pmu_fw_ctr_read_hi(vcpu, cidx, &retdata->out_val);
• if (ret == -EINVAL)

• retdata->err_val = SBI_ERR_INVALID_PARAM;
  

• return 0;

I see this follows the pattern we have with kvm_riscv_vcpu_pmu_ctr_read and pmu_ctr_read, but I wonder if we really need the kvm_riscv_vcpu_pmu_ctr_read() and kvm_riscv_vcpu_pmu_fw_ctr_read_hi() wrapper functions?

+}

int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx, struct kvm_vcpu_sbi_return *retdata) { @@ -775,7 +810,7 @@ void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu) pmc->cinfo.csr = CSR_CYCLE + i; } else { pmc->cinfo.type = SBI_PMU_CTR_TYPE_FW;

• 	pmc->cinfo.width = BITS_PER_LONG - 1;
  

• 	pmc->cinfo.width = 63;
  

  } }

diff --git a/arch/riscv/kvm/vcpu_sbi_pmu.c b/arch/riscv/kvm/vcpu_sbi_pmu.c index 9f61136e4bb1..58a0e5587e2a 100644 --- a/arch/riscv/kvm/vcpu_sbi_pmu.c +++ b/arch/riscv/kvm/vcpu_sbi_pmu.c @@ -64,6 +64,12 @@ static int kvm_sbi_ext_pmu_handler(struct kvm_vcpu *vcpu, struct kvm_run *run, case SBI_EXT_PMU_COUNTER_FW_READ: ret = kvm_riscv_vcpu_pmu_ctr_read(vcpu, cp->a0, retdata); break;

• case SBI_EXT_PMU_COUNTER_FW_READ_HI:

• if (IS_ENABLED(CONFIG_32BIT))
  

• 	ret = kvm_riscv_vcpu_pmu_fw_ctr_read_hi(vcpu, cp->a0, retdata);
  

• else
  

• 	retdata->out_val = 0;
  

• break;
  

  case SBI_EXT_PMU_SNAPSHOT_SET_SHMEM: ret = kvm_riscv_vcpu_pmu_setup_snapshot(vcpu, cp->a0, cp->a1, cp->a2, retdata); break;

-- 2.34.1

Thanks, drew