diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h index 24585304c02b..7ee47b83c80d 100644 --- a/arch/riscv/include/asm/kvm_host.h +++ b/arch/riscv/include/asm/kvm_host.h @@ -273,6 +273,9 @@ struct kvm_vcpu_arch { /* 'static' configurations which are set only once */ struct kvm_vcpu_config cfg; + /* Indicates modified guest CSRs */ + bool csr_dirty; + /* SBI steal-time accounting */ struct { gpa_t shmem; diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c index fdd99ac1e714..1d5c777eba80 100644 --- a/arch/riscv/kvm/vcpu.c +++ b/arch/riscv/kvm/vcpu.c @@ -24,6 +24,8 @@ #define CREATE_TRACE_POINTS #include "trace.h" +static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_former_vcpu); + const struct kvm_stats_desc kvm_vcpu_stats_desc[] = { KVM_GENERIC_VCPU_STATS(), STATS_DESC_COUNTER(VCPU, ecall_exit_stat), @@ -537,6 +539,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, vcpu->arch.cfg.hedeleg |= BIT(EXC_BREAKPOINT); } + vcpu->arch.csr_dirty = true; + return 0; } @@ -581,6 +585,21 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr; struct kvm_vcpu_config *cfg = &vcpu->arch.cfg; + /* + * If VCPU is being reloaded on the same physical CPU and no + * other KVM VCPU has run on this CPU since it was last put, + * we can skip the expensive CSR and HGATP writes. + * + * Note: If a new CSR is added to this fast-path skip block, + * make sure that 'csr_dirty' is set to true in any + * ioctl (e.g., KVM_SET_ONE_REG) that modifies it. + */ + if (vcpu != __this_cpu_read(kvm_former_vcpu)) + __this_cpu_write(kvm_former_vcpu, vcpu); + else if (vcpu->arch.last_exit_cpu == cpu && !vcpu->arch.csr_dirty) + goto csr_restore_done; + + vcpu->arch.csr_dirty = false; if (kvm_riscv_nacl_sync_csr_available()) { nsh = nacl_shmem(); nacl_csr_write(nsh, CSR_VSSTATUS, csr->vsstatus); @@ -624,6 +643,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_riscv_mmu_update_hgatp(vcpu); + kvm_riscv_vcpu_aia_load(vcpu, cpu); + +csr_restore_done: kvm_riscv_vcpu_timer_restore(vcpu); kvm_riscv_vcpu_host_fp_save(&vcpu->arch.host_context); @@ -633,8 +655,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) kvm_riscv_vcpu_guest_vector_restore(&vcpu->arch.guest_context, vcpu->arch.isa); - kvm_riscv_vcpu_aia_load(vcpu, cpu); - kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); vcpu->cpu = cpu; diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c index 45ecc0082e90..97fa72ba47c1 100644 --- a/arch/riscv/kvm/vcpu_onereg.c +++ b/arch/riscv/kvm/vcpu_onereg.c @@ -670,6 +670,8 @@ static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu, if (rc) return rc; + vcpu->arch.csr_dirty = true; + return 0; }