Emulating the vGIC means emulating the dreaded Maintenance Interrupt. This is a two-pronged problem: - while running L2, getting an MI translates into an MI injected in the L1 based on the state of the HW. - while running L1, we must accurately reflect the state of the MI line, based on the in-memory state. The MI INTID is added to the distributor, as expected on any virtualisation-capable implementation, and further patches will allow its configuration. Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> --- arch/arm64/kvm/arm.c | 6 ++++ arch/arm64/kvm/vgic/vgic-init.c | 22 ++++++++++++++ arch/arm64/kvm/vgic/vgic-v3-nested.c | 45 ++++++++++++++++++++++++++++ arch/arm64/kvm/vgic/vgic.c | 9 ++++++ arch/arm64/kvm/vgic/vgic.h | 2 ++ include/kvm/arm_vgic.h | 4 +++ 6 files changed, 88 insertions(+) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 5e353b2c225b4..756cc4e74e10f 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -824,6 +824,12 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) if (ret) return ret; + if (vcpu_has_nv(vcpu)) { + ret = kvm_vgic_vcpu_nv_init(vcpu); + if (ret) + return ret; + } + /* * This needs to happen after any restriction has been applied * to the feature set. diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index bc7e22ab5d812..d2724315a70e9 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -180,6 +180,20 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis) return 0; } +int kvm_vgic_vcpu_nv_init(struct kvm_vcpu *vcpu) +{ + int ret; + + guard(mutex)(&vcpu->kvm->arch.config_lock); + + /* Cope with vintage userspace. Maybe we should fail instead */ + if (vcpu->kvm->arch.vgic.maint_irq == 0) + vcpu->kvm->arch.vgic.maint_irq = kvm_vgic_global_state.maint_irq; + ret = kvm_vgic_set_owner(vcpu, vcpu->kvm->arch.vgic.maint_irq, vcpu); + + return ret; +} + static int vgic_allocate_private_irqs_locked(struct kvm_vcpu *vcpu) { struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; @@ -588,12 +602,20 @@ void kvm_vgic_cpu_down(void) static irqreturn_t vgic_maintenance_handler(int irq, void *data) { + struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)data; + /* * We cannot rely on the vgic maintenance interrupt to be * delivered synchronously. This means we can only use it to * exit the VM, and we perform the handling of EOIed * interrupts on the exit path (see vgic_fold_lr_state). + * + * Of course, NV throws a wrench in this plan, and needs + * something special. */ + if (vcpu && vgic_state_is_nested(vcpu)) + vgic_v3_handle_nested_maint_irq(vcpu); + return IRQ_HANDLED; } diff --git a/arch/arm64/kvm/vgic/vgic-v3-nested.c b/arch/arm64/kvm/vgic/vgic-v3-nested.c index 3d80bfb37de00..fba499a20aec8 100644 --- a/arch/arm64/kvm/vgic/vgic-v3-nested.c +++ b/arch/arm64/kvm/vgic/vgic-v3-nested.c @@ -73,6 +73,24 @@ static DEFINE_PER_CPU(struct shadow_if, shadow_if); * interrupt. The L0 active state will be cleared by the HW if the L1 * interrupt was itself backed by a HW interrupt. * + * Maintenance Interrupt (MI) management: + * + * Since the L2 guest runs the vgic in its full glory, MIs get delivered and + * used as a handover point between L2 and L1. + * + * - on delivery of a MI to L0 while L2 is running: make the L1 MI pending, + * and let it rip. This will initiate a vcpu_put() on L2, and allow L1 to + * run and process the MI. + * + * - L1 MI is a fully virtual interrupt, not linked to the host's MI. Its + * state must be computed at each entry/exit of the guest, much like we do + * it for the PMU interrupt. + * + * - because most of the ICH_*_EL2 registers live in the VNCR page, the + * quality of emulation is poor: L1 can setup the vgic so that an MI would + * immediately fire, and not observe anything until the next exit. Trying + * to read ICH_MISR_EL2 would do the trick, for example. + * * System register emulation: * * We get two classes of registers: @@ -341,3 +359,30 @@ void vgic_v3_put_nested(struct kvm_vcpu *vcpu) shadow_if->lr_map = 0; } + +/* + * If we exit a L2 VM with a pending maintenance interrupt from the GIC, + * then we need to forward this to L1 so that it can re-sync the appropriate + * LRs and sample level triggered interrupts again. + */ +void vgic_v3_handle_nested_maint_irq(struct kvm_vcpu *vcpu) +{ + bool state = read_sysreg_s(SYS_ICH_MISR_EL2); + + /* This will force a switch back to L1 if the level is high */ + kvm_vgic_inject_irq(vcpu->kvm, vcpu, + vcpu->kvm->arch.vgic.maint_irq, state, vcpu); + + sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EL2_En, 0); +} + +void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu) +{ + bool level; + + level = __vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_En; + if (level) + level &= vgic_v3_get_misr(vcpu); + kvm_vgic_inject_irq(vcpu->kvm, vcpu, + vcpu->kvm->arch.vgic.maint_irq, level, vcpu); +} diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c index 9734a71b85611..8f8096d489252 100644 --- a/arch/arm64/kvm/vgic/vgic.c +++ b/arch/arm64/kvm/vgic/vgic.c @@ -878,6 +878,9 @@ void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu) return; } + if (vcpu_has_nv(vcpu)) + vgic_v3_nested_update_mi(vcpu); + /* An empty ap_list_head implies used_lrs == 0 */ if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head)) return; @@ -921,6 +924,9 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu) * * - Otherwise, do exactly *NOTHING*. The guest state is * already loaded, and we can carry on with running it. + * + * If we have NV, but are not in a nested state, compute the + * maintenance interrupt state, as it may fire. */ if (vgic_state_is_nested(vcpu)) { if (kvm_vgic_vcpu_pending_irq(vcpu)) @@ -929,6 +935,9 @@ void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu) return; } + if (vcpu_has_nv(vcpu)) + vgic_v3_nested_update_mi(vcpu); + /* * If there are no virtual interrupts active or pending for this * VCPU, then there is no work to do and we can bail out without diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h index cf0c084e5d347..0c5a63712702b 100644 --- a/arch/arm64/kvm/vgic/vgic.h +++ b/arch/arm64/kvm/vgic/vgic.h @@ -356,5 +356,7 @@ static inline bool kvm_has_gicv3(struct kvm *kvm) void vgic_v3_sync_nested(struct kvm_vcpu *vcpu); void vgic_v3_load_nested(struct kvm_vcpu *vcpu); void vgic_v3_put_nested(struct kvm_vcpu *vcpu); +void vgic_v3_handle_nested_maint_irq(struct kvm_vcpu *vcpu); +void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu); #endif diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h index 1b373cb870fe4..b33166f05124c 100644 --- a/include/kvm/arm_vgic.h +++ b/include/kvm/arm_vgic.h @@ -249,6 +249,9 @@ struct vgic_dist { int nr_spis; + /* The GIC maintenance IRQ for nested hypervisors. */ + u32 maint_irq; + /* base addresses in guest physical address space: */ gpa_t vgic_dist_base; /* distributor */ union { @@ -369,6 +372,7 @@ extern struct static_key_false vgic_v3_cpuif_trap; int kvm_set_legacy_vgic_v2_addr(struct kvm *kvm, struct kvm_arm_device_addr *dev_addr); void kvm_vgic_early_init(struct kvm *kvm); int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu); +int kvm_vgic_vcpu_nv_init(struct kvm_vcpu *vcpu); int kvm_vgic_create(struct kvm *kvm, u32 type); void kvm_vgic_destroy(struct kvm *kvm); void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu); -- 2.39.2