On Fri, Jan 25, 2019 at 10:46:55AM +0100, Christoffer Dall wrote:
> We are currently not implementing the PSCI spec completely, as we do not
> take handle the situation where two VCPUs are attempting to turn on a
> third VCPU at the same time. The PSCI implementation should make sure
> that only one requesting VCPU wins the race and that the other receives
> PSCI_RET_ON_PENDING.
>
> Implement this by changing the VCPU power state to a tristate enum and
> ensure only a single VCPU can turn on another VCPU at a given time using
> a cmpxchg operation.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 10 ++++++++--
> arch/arm64/include/asm/kvm_host.h | 10 ++++++++--
> virt/kvm/arm/arm.c | 24 +++++++++++++++---------
> virt/kvm/arm/psci.c | 21 ++++++++++++++-------
> 4 files changed, 45 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index b1cfae222441..4dc47fea1ac8 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -157,6 +157,12 @@ struct vcpu_reset_state {
> bool reset;
> };
>
> +enum vcpu_power_state {
> + KVM_ARM_VCPU_OFF,
> + KVM_ARM_VCPU_ON_PENDING,
> + KVM_ARM_VCPU_ON,
> +};
> +
> struct kvm_vcpu_arch {
> struct kvm_cpu_context ctxt;
>
> @@ -184,8 +190,8 @@ struct kvm_vcpu_arch {
> * here.
> */
>
> - /* vcpu power-off state */
> - bool power_off;
> + /* vcpu power state */
> + enum vcpu_power_state power_state;
>
> /* Don't run the guest (internal implementation need) */
> bool pause;
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index d43b13421987..0647a409657b 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -218,6 +218,12 @@ struct vcpu_reset_state {
> bool reset;
> };
>
> +enum vcpu_power_state {
> + KVM_ARM_VCPU_OFF,
> + KVM_ARM_VCPU_ON_PENDING,
> + KVM_ARM_VCPU_ON,
> +};
> +
> struct kvm_vcpu_arch {
> struct kvm_cpu_context ctxt;
>
> @@ -285,8 +291,8 @@ struct kvm_vcpu_arch {
> u32 mdscr_el1;
> } guest_debug_preserved;
>
> - /* vcpu power-off state */
> - bool power_off;
> + /* vcpu power state */
> + enum vcpu_power_state power_state;
>
> /* Don't run the guest (internal implementation need) */
> bool pause;
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 785076176814..1e3195155860 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -411,7 +411,7 @@ static void vcpu_power_off(struct kvm_vcpu *vcpu)
> int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
> struct kvm_mp_state *mp_state)
> {
> - if (vcpu->arch.power_off)
> + if (vcpu->arch.power_state != KVM_ARM_VCPU_ON)
> mp_state->mp_state = KVM_MP_STATE_STOPPED;
> else
> mp_state->mp_state = KVM_MP_STATE_RUNNABLE;
> @@ -426,7 +426,7 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
>
> switch (mp_state->mp_state) {
> case KVM_MP_STATE_RUNNABLE:
> - vcpu->arch.power_off = false;
> + vcpu->arch.power_state = KVM_ARM_VCPU_ON;
> break;
> case KVM_MP_STATE_STOPPED:
> vcpu_power_off(vcpu);
> @@ -448,8 +448,9 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> int kvm_arch_vcpu_runnable(struct kvm_vcpu *v)
> {
> bool irq_lines = *vcpu_hcr(v) & (HCR_VI | HCR_VF);
> - return ((irq_lines || kvm_vgic_vcpu_pending_irq(v))
> - && !v->arch.power_off && !v->arch.pause);
> + return (irq_lines || kvm_vgic_vcpu_pending_irq(v)) &&
> + v->arch.power_state == KVM_ARM_VCPU_ON &&
> + !v->arch.pause;
> }
>
> bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> @@ -614,14 +615,19 @@ void kvm_arm_resume_guest(struct kvm *kvm)
> }
> }
>
> +static bool vcpu_sleeping(struct kvm_vcpu *vcpu)
> +{
> + return vcpu->arch.power_state != KVM_ARM_VCPU_ON ||
> + vcpu->arch.pause;
> +}
> +
> static void vcpu_req_sleep(struct kvm_vcpu *vcpu)
> {
> struct swait_queue_head *wq = kvm_arch_vcpu_wq(vcpu);
>
> - swait_event_interruptible_exclusive(*wq, ((!vcpu->arch.power_off) &&
> - (!vcpu->arch.pause)));
> + swait_event_interruptible_exclusive(*wq, !vcpu_sleeping(vcpu));
>
> - if (vcpu->arch.power_off || vcpu->arch.pause) {
> + if (vcpu_sleeping(vcpu)) {
> /* Awaken to handle a signal, request we sleep again later. */
> kvm_make_request(KVM_REQ_SLEEP, vcpu);
> }
> @@ -646,7 +652,7 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
> vcpu_req_sleep(vcpu);
>
> if (kvm_check_request(KVM_REQ_VCPU_OFF, vcpu)) {
> - vcpu->arch.power_off = true;
> + vcpu->arch.power_state = KVM_ARM_VCPU_OFF;
> vcpu_req_sleep(vcpu);
> }
>
> @@ -1016,7 +1022,7 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
> if (test_bit(KVM_ARM_VCPU_POWER_OFF, vcpu->arch.features))
> vcpu_power_off(vcpu);
> else
> - vcpu->arch.power_off = false;
> + vcpu->arch.power_state = KVM_ARM_VCPU_ON;
>
> return 0;
> }
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
> index 20255319e193..5c2d9eeb810c 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -106,6 +106,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> struct kvm *kvm = source_vcpu->kvm;
> struct kvm_vcpu *vcpu = NULL;
> unsigned long cpu_id;
> + enum vcpu_power_state old_power_state;
>
> cpu_id = smccc_get_arg1(source_vcpu) & MPIDR_HWID_BITMASK;
> if (vcpu_mode_is_32bit(source_vcpu))
> @@ -119,12 +120,18 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> */
> if (!vcpu)
> return PSCI_RET_INVALID_PARAMS;
> - if (!vcpu->arch.power_off) {
> - if (kvm_psci_version(source_vcpu, kvm) != KVM_ARM_PSCI_0_1)
> - return PSCI_RET_ALREADY_ON;
> - else
> + old_power_state = cmpxchg(&vcpu->arch.power_state,
> + KVM_ARM_VCPU_OFF,
> + KVM_ARM_VCPU_ON_PENDING);
> +
> + if (old_power_state != KVM_ARM_VCPU_OFF &&
> + kvm_psci_version(source_vcpu, kvm) == KVM_ARM_PSCI_0_1)
> return PSCI_RET_INVALID_PARAMS;
> - }
> +
> + if (old_power_state == KVM_ARM_VCPU_ON_PENDING)
> + return PSCI_RET_ON_PENDING;
> + else if (old_power_state == KVM_ARM_VCPU_ON)
> + return PSCI_RET_ALREADY_ON;
>
> reset_state = &vcpu->arch.reset_state;
>
> @@ -148,7 +155,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> */
> smp_wmb();
>
> - vcpu->arch.power_off = false;
> + vcpu->arch.power_state = KVM_ARM_VCPU_ON;
> kvm_vcpu_wake_up(vcpu);
>
> return PSCI_RET_SUCCESS;
> @@ -183,7 +190,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
> mpidr = kvm_vcpu_get_mpidr_aff(tmp);
> if ((mpidr & target_affinity_mask) == target_affinity) {
> matching_cpus++;
> - if (!tmp->arch.power_off)
> + if (tmp->arch.power_state == KVM_ARM_VCPU_ON)
> return PSCI_0_2_AFFINITY_LEVEL_ON;
> }
> }
> --
> 2.18.0
>
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
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