[PATCH v5 4/4] RISC-V: KVM: Support sstc extension
Anup Patel
anup at brainfault.org
Wed Jul 20 21:33:38 PDT 2022
On Thu, Jul 21, 2022 at 12:53 AM Atish Patra <atishp at rivosinc.com> wrote:
>
> Sstc extension allows the guest to program the vstimecmp CSR directly
> instead of making an SBI call to the hypervisor to program the next
> event. The timer interrupt is also directly injected to the guest by
> the hardware in this case. To maintain backward compatibility, the
> hypervisors also update the vstimecmp in an SBI set_time call if
> the hardware supports it. Thus, the older kernels in guest also
> take advantage of the sstc extension.
>
> Reviewed-by: Anup Patel <anup at brainfault.org>
> Signed-off-by: Atish Patra <atishp at rivosinc.com>
> ---
> arch/riscv/include/asm/kvm_vcpu_timer.h | 7 ++
> arch/riscv/include/uapi/asm/kvm.h | 1 +
> arch/riscv/kvm/vcpu.c | 7 +-
> arch/riscv/kvm/vcpu_timer.c | 144 +++++++++++++++++++++++-
> 4 files changed, 152 insertions(+), 7 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_vcpu_timer.h b/arch/riscv/include/asm/kvm_vcpu_timer.h
> index 50138e2eb91b..0d8fdb8ec63a 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_timer.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_timer.h
> @@ -28,6 +28,11 @@ struct kvm_vcpu_timer {
> u64 next_cycles;
> /* Underlying hrtimer instance */
> struct hrtimer hrt;
> +
> + /* Flag to check if sstc is enabled or not */
> + bool sstc_enabled;
> + /* A function pointer to switch between stimecmp or hrtimer at runtime */
> + int (*timer_next_event)(struct kvm_vcpu *vcpu, u64 ncycles);
> };
>
> int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles);
> @@ -40,5 +45,7 @@ int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu);
> int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu);
> void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu);
> void kvm_riscv_guest_timer_init(struct kvm *kvm);
> +void kvm_riscv_vcpu_timer_save(struct kvm_vcpu *vcpu);
> +bool kvm_riscv_vcpu_timer_pending(struct kvm_vcpu *vcpu);
>
> #endif
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index 24b2a6e27698..9ac3dbaf0b0f 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -96,6 +96,7 @@ enum KVM_RISCV_ISA_EXT_ID {
> KVM_RISCV_ISA_EXT_H,
> KVM_RISCV_ISA_EXT_I,
> KVM_RISCV_ISA_EXT_M,
> + KVM_RISCV_ISA_EXT_SSTC,
Please don't add a new ISA ext register in-between to maintain
UAPI compatibility.
> KVM_RISCV_ISA_EXT_SVPBMT,
> KVM_RISCV_ISA_EXT_MAX,
> };
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 5d271b597613..9ee6ad376eb2 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -51,6 +51,7 @@ static const unsigned long kvm_isa_ext_arr[] = {
> RISCV_ISA_EXT_h,
> RISCV_ISA_EXT_i,
> RISCV_ISA_EXT_m,
> + RISCV_ISA_EXT_SSTC,
Move this at the end of array as-per above.
> RISCV_ISA_EXT_SVPBMT,
> };
>
> @@ -203,7 +204,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
>
> int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
> {
> - return kvm_riscv_vcpu_has_interrupts(vcpu, 1UL << IRQ_VS_TIMER);
> + return kvm_riscv_vcpu_timer_pending(vcpu);
> }
>
> void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
> @@ -785,6 +786,8 @@ static void kvm_riscv_vcpu_update_config(const unsigned long *isa)
> if (__riscv_isa_extension_available(isa, RISCV_ISA_EXT_SVPBMT))
> henvcfg |= ENVCFG_PBMTE;
>
> + if (__riscv_isa_extension_available(isa, RISCV_ISA_EXT_SSTC))
> + henvcfg |= ENVCFG_STCE;
> csr_write(CSR_HENVCFG, henvcfg);
> #ifdef CONFIG_32BIT
> csr_write(CSR_HENVCFGH, henvcfg >> 32);
> @@ -828,6 +831,8 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> vcpu->arch.isa);
> kvm_riscv_vcpu_host_fp_restore(&vcpu->arch.host_context);
>
> + kvm_riscv_vcpu_timer_save(vcpu);
> +
> csr->vsstatus = csr_read(CSR_VSSTATUS);
> csr->vsie = csr_read(CSR_VSIE);
> csr->vstvec = csr_read(CSR_VSTVEC);
> diff --git a/arch/riscv/kvm/vcpu_timer.c b/arch/riscv/kvm/vcpu_timer.c
> index 595043857049..16f50c46ba39 100644
> --- a/arch/riscv/kvm/vcpu_timer.c
> +++ b/arch/riscv/kvm/vcpu_timer.c
> @@ -69,7 +69,18 @@ static int kvm_riscv_vcpu_timer_cancel(struct kvm_vcpu_timer *t)
> return 0;
> }
>
> -int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
> +static int kvm_riscv_vcpu_update_vstimecmp(struct kvm_vcpu *vcpu, u64 ncycles)
> +{
> +#if defined(CONFIG_32BIT)
> + csr_write(CSR_VSTIMECMP, ncycles & 0xFFFFFFFF);
> + csr_write(CSR_VSTIMECMPH, ncycles >> 32);
> +#else
> + csr_write(CSR_VSTIMECMP, ncycles);
> +#endif
> + return 0;
> +}
> +
> +static int kvm_riscv_vcpu_update_hrtimer(struct kvm_vcpu *vcpu, u64 ncycles)
> {
> struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
> @@ -88,6 +99,65 @@ int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
> return 0;
> }
>
> +int kvm_riscv_vcpu_timer_next_event(struct kvm_vcpu *vcpu, u64 ncycles)
> +{
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> +
> + return t->timer_next_event(vcpu, ncycles);
> +}
> +
> +static enum hrtimer_restart kvm_riscv_vcpu_vstimer_expired(struct hrtimer *h)
> +{
> + u64 delta_ns;
> + struct kvm_vcpu_timer *t = container_of(h, struct kvm_vcpu_timer, hrt);
> + struct kvm_vcpu *vcpu = container_of(t, struct kvm_vcpu, arch.timer);
> + struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
> +
> + if (kvm_riscv_current_cycles(gt) < t->next_cycles) {
> + delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
> + hrtimer_forward_now(&t->hrt, ktime_set(0, delta_ns));
> + return HRTIMER_RESTART;
> + }
> +
> + t->next_set = false;
> + kvm_vcpu_kick(vcpu);
> +
> + return HRTIMER_NORESTART;
> +}
> +
> +bool kvm_riscv_vcpu_timer_pending(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> + struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
> +
> + if (!kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t) ||
> + kvm_riscv_vcpu_has_interrupts(vcpu, 1UL << IRQ_VS_TIMER))
> + return true;
> + else
> + return false;
> +}
> +
> +static void kvm_riscv_vcpu_timer_blocking(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> + struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
> + u64 delta_ns;
> +
> + if (!t->init_done)
> + return;
> +
> + delta_ns = kvm_riscv_delta_cycles2ns(t->next_cycles, gt, t);
> + if (delta_ns) {
> + hrtimer_start(&t->hrt, ktime_set(0, delta_ns), HRTIMER_MODE_REL);
> + t->next_set = true;
> + }
> +}
> +
> +static void kvm_riscv_vcpu_timer_unblocking(struct kvm_vcpu *vcpu)
> +{
> + kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
> +}
> +
> int kvm_riscv_vcpu_get_reg_timer(struct kvm_vcpu *vcpu,
> const struct kvm_one_reg *reg)
> {
> @@ -180,10 +250,20 @@ int kvm_riscv_vcpu_timer_init(struct kvm_vcpu *vcpu)
> return -EINVAL;
>
> hrtimer_init(&t->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> - t->hrt.function = kvm_riscv_vcpu_hrtimer_expired;
> t->init_done = true;
> t->next_set = false;
>
> + /* Enable sstc for every vcpu if available in hardware */
> + if (riscv_isa_extension_available(NULL, SSTC)) {
> + t->sstc_enabled = true;
> + t->hrt.function = kvm_riscv_vcpu_vstimer_expired;
> + t->timer_next_event = kvm_riscv_vcpu_update_vstimecmp;
> + } else {
> + t->sstc_enabled = false;
> + t->hrt.function = kvm_riscv_vcpu_hrtimer_expired;
> + t->timer_next_event = kvm_riscv_vcpu_update_hrtimer;
> + }
> +
> return 0;
> }
>
> @@ -199,21 +279,73 @@ int kvm_riscv_vcpu_timer_deinit(struct kvm_vcpu *vcpu)
>
> int kvm_riscv_vcpu_timer_reset(struct kvm_vcpu *vcpu)
> {
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> +
> + t->next_cycles = -1ULL;
> return kvm_riscv_vcpu_timer_cancel(&vcpu->arch.timer);
> }
>
> -void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
> +static void kvm_riscv_vcpu_update_timedelta(struct kvm_vcpu *vcpu)
> {
> struct kvm_guest_timer *gt = &vcpu->kvm->arch.timer;
>
> -#ifdef CONFIG_64BIT
> - csr_write(CSR_HTIMEDELTA, gt->time_delta);
> -#else
> +#if defined(CONFIG_32BIT)
> csr_write(CSR_HTIMEDELTA, (u32)(gt->time_delta));
> csr_write(CSR_HTIMEDELTAH, (u32)(gt->time_delta >> 32));
> +#else
> + csr_write(CSR_HTIMEDELTA, gt->time_delta);
> #endif
> }
>
> +void kvm_riscv_vcpu_timer_restore(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_vcpu_csr *csr;
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> +
> + kvm_riscv_vcpu_update_timedelta(vcpu);
> +
> + if (!t->sstc_enabled)
> + return;
> +
> + csr = &vcpu->arch.guest_csr;
> +#if defined(CONFIG_32BIT)
> + csr_write(CSR_VSTIMECMP, (u32)t->next_cycles);
> + csr_write(CSR_VSTIMECMPH, (u32)(t->next_cycles >> 32));
> +#else
> + csr_write(CSR_VSTIMECMP, t->next_cycles);
> +#endif
> +
> + /* timer should be enabled for the remaining operations */
> + if (unlikely(!t->init_done))
> + return;
> +
> + kvm_riscv_vcpu_timer_unblocking(vcpu);
> +}
> +
> +void kvm_riscv_vcpu_timer_save(struct kvm_vcpu *vcpu)
> +{
> + struct kvm_vcpu_csr *csr;
> + struct kvm_vcpu_timer *t = &vcpu->arch.timer;
> +
> + if (!t->sstc_enabled)
> + return;
> +
> + csr = &vcpu->arch.guest_csr;
> + t = &vcpu->arch.timer;
> +#if defined(CONFIG_32BIT)
> + t->next_cycles = csr_read(CSR_VSTIMECMP);
> + t->next_cycles |= (u64)csr_read(CSR_VSTIMECMPH) << 32;
> +#else
> + t->next_cycles = csr_read(CSR_VSTIMECMP);
> +#endif
> + /* timer should be enabled for the remaining operations */
> + if (unlikely(!t->init_done))
> + return;
> +
> + if (kvm_vcpu_is_blocking(vcpu))
> + kvm_riscv_vcpu_timer_blocking(vcpu);
> +}
> +
> void kvm_riscv_guest_timer_init(struct kvm *kvm)
> {
> struct kvm_guest_timer *gt = &kvm->arch.timer;
> --
> 2.25.1
>
Regards,
Anup
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