6.6-stable review patch. If anyone has any objections, please let me know.
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From: Atish Patra atishp@rivosinc.com
[ Upstream commit 7d1ffc8b087e97dbe1985912c7a2d00e53cea169 ]
Currently, KVM traps & emulates PMU counter access only if SBI PMU is available as the guest can only configure/read PMU counters via SBI only. However, if SBI PMU is not enabled in the host, the guest will fallback to the legacy PMU which will try to access cycle/instret and result in an illegal instruction trap which is not desired.
KVM can allow dummy emulation of cycle/instret only for the guest if SBI PMU is not enabled in the host. The dummy emulation will still return zero as we don't to expose the host counter values from a guest using legacy PMU.
Fixes: a9ac6c37521f ("RISC-V: KVM: Implement trap & emulate for hpmcounters") Signed-off-by: Atish Patra atishp@rivosinc.com Link: https://lore.kernel.org/r/20240816-kvm_pmu_fixes-v1-1-cdfce386dd93@rivosinc.... Signed-off-by: Anup Patel anup@brainfault.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/include/asm/kvm_vcpu_pmu.h | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/kvm_vcpu_pmu.h b/arch/riscv/include/asm/kvm_vcpu_pmu.h index 395518a1664e0..6823271bce322 100644 --- a/arch/riscv/include/asm/kvm_vcpu_pmu.h +++ b/arch/riscv/include/asm/kvm_vcpu_pmu.h @@ -10,6 +10,7 @@ #define __KVM_VCPU_RISCV_PMU_H
#include <linux/perf/riscv_pmu.h> +#include <asm/kvm_vcpu_insn.h> #include <asm/sbi.h>
#ifdef CONFIG_RISCV_PMU_SBI @@ -92,8 +93,20 @@ void kvm_riscv_vcpu_pmu_reset(struct kvm_vcpu *vcpu); struct kvm_pmu { };
+static inline int kvm_riscv_vcpu_pmu_read_legacy(struct kvm_vcpu *vcpu, unsigned int csr_num, + unsigned long *val, unsigned long new_val, + unsigned long wr_mask) +{ + if (csr_num == CSR_CYCLE || csr_num == CSR_INSTRET) { + *val = 0; + return KVM_INSN_CONTINUE_NEXT_SEPC; + } else { + return KVM_INSN_ILLEGAL_TRAP; + } +} + #define KVM_RISCV_VCPU_HPMCOUNTER_CSR_FUNCS \ -{.base = 0, .count = 0, .func = NULL }, +{.base = CSR_CYCLE, .count = 3, .func = kvm_riscv_vcpu_pmu_read_legacy },
static inline void kvm_riscv_vcpu_pmu_init(struct kvm_vcpu *vcpu) {} static inline int kvm_riscv_vcpu_pmu_incr_fw(struct kvm_vcpu *vcpu, unsigned long fid)