RISC-V: KVM: Improve firmware counter read function

Rename the function to indicate that it is meant for firmware
counter read. While at it, add a range sanity check for it as
well.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20240420151741.962500-17-atishp@rivosinc.com
Signed-off-by: Anup Patel <anup@brainfault.org>

Author: atishp04

arch/riscv/include/asm/kvm_vcpu_pmu.h

@@ -89,7 +89,7 @@ int kvm_riscv_vcpu_pmu_ctr_cfg_match(struct kvm_vcpu *vcpu, unsigned long ctr_ba
 				     unsigned long ctr_mask, unsigned long flags,
 				     unsigned long eidx, u64 evtdata,
 				     struct kvm_vcpu_sbi_return *retdata);
-int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
+int kvm_riscv_vcpu_pmu_fw_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);

arch/riscv/kvm/vcpu_pmu.c

@@ -235,6 +235,11 @@ static int pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
 	u64 enabled, running;
 	int fevent_code;
 
+	if (cidx >= kvm_pmu_num_counters(kvpmu) || cidx == 1) {
+		pr_warn("Invalid counter id [%ld] during read\n", cidx);
+		return -EINVAL;
+	}
+
 	pmc = &kvpmu->pmc[cidx];
 
 	if (pmc->cinfo.type == SBI_PMU_CTR_TYPE_FW) {
@@ -747,7 +752,7 @@ int kvm_riscv_vcpu_pmu_fw_ctr_read_hi(struct kvm_vcpu *vcpu, unsigned long cidx,
 	return 0;
 }
 
-int kvm_riscv_vcpu_pmu_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
+int kvm_riscv_vcpu_pmu_fw_ctr_read(struct kvm_vcpu *vcpu, unsigned long cidx,
 				struct kvm_vcpu_sbi_return *retdata)
 {
 	int ret;

arch/riscv/kvm/vcpu_sbi_pmu.c

@@ -62,7 +62,7 @@ static int kvm_sbi_ext_pmu_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		ret = kvm_riscv_vcpu_pmu_ctr_stop(vcpu, cp->a0, cp->a1, cp->a2, retdata);
 		break;
 	case SBI_EXT_PMU_COUNTER_FW_READ:
-		ret = kvm_riscv_vcpu_pmu_ctr_read(vcpu, cp->a0, retdata);
+		ret = kvm_riscv_vcpu_pmu_fw_ctr_read(vcpu, cp->a0, retdata);
 		break;
 	case SBI_EXT_PMU_COUNTER_FW_READ_HI:
 		if (IS_ENABLED(CONFIG_32BIT))