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Subject[RFC v6 16/16] KVM: arm/arm64: vgic: forwarding control
Date
This patch sets __KVM_HAVE_ARCH_KVM_VFIO_FORWARD and implements
kvm_arch_set_forward for ARM/ARM64.

As a result the KVM-VFIO device now allows to forward/unforward a
VFIO device IRQ on ARM.

kvm_arch_set_forward and kvm_arch_unset_forward mostly take care of
VGIC programming: physical IRQ/guest IRQ mapping, list register cleanup,
VGIC state machine.

Signed-off-by: Eric Auger <eric.auger@linaro.org>

---

v4 -> v5:
- fix arm64 compilation issues, ie. also defines
__KVM_HAVE_ARCH_HALT_GUEST for arm64

v3 -> v4:
- code originally located in kvm_vfio_arm.c
- kvm_arch_vfio_{set|unset}_forward renamed into
kvm_arch_{set|unset}_forward
- split into 2 functions (set/unset) since unset does not fail anymore
- unset can be invoked at whatever time. Extra care is taken to handle
transition in VGIC state machine, LR cleanup, ...

v2 -> v3:
- renaming of kvm_arch_set_fwd_state into kvm_arch_vfio_set_forward
- takes a bool arg instead of kvm_fwd_irq_action enum
- removal of KVM_VFIO_IRQ_CLEANUP
- platform device check now happens here
- more precise errors returned
- irq_eoi handled externally to this patch (VGIC)
- correct enable_irq bug done twice
- reword the commit message
- correct check of platform_bus_type
- use raw_spin_lock_irqsave and check the validity of the handler
---
arch/arm/include/asm/kvm_host.h | 1 +
arch/arm64/include/asm/kvm_host.h | 1 +
virt/kvm/arm/vgic.c | 190 ++++++++++++++++++++++++++++++++++++++
3 files changed, 192 insertions(+)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index b829f93..8e3fd7f 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -29,6 +29,7 @@

#define __KVM_HAVE_ARCH_INTC_INITIALIZED
#define __KVM_HAVE_ARCH_HALT_GUEST
+#define __KVM_HAVE_ARCH_KVM_VFIO_FORWARD

#if defined(CONFIG_KVM_ARM_MAX_VCPUS)
#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ffcc698..9be392a 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -30,6 +30,7 @@

#define __KVM_HAVE_ARCH_INTC_INITIALIZED
#define __KVM_HAVE_ARCH_HALT_GUEST
+#define __KVM_HAVE_ARCH_KVM_VFIO_FORWARD

#if defined(CONFIG_KVM_ARM_MAX_VCPUS)
#define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index f345c41..c0ac151 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -2133,3 +2133,193 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
{
return 0;
}
+
+/**
+ * kvm_arch_set_forward - Set forwarding for a given IRQ
+ *
+ * @kvm: handle to the VM
+ * @host_irq: physical IRQ number
+ * @guest_irq: virtual IRQ number
+ *
+ * This function is supposed to be called only if the IRQ
+ * is not in progress: ie. not active at VGIC level and not
+ * currently under injection in the KVM.
+ */
+int kvm_arch_set_forward(struct kvm *kvm, unsigned int host_irq,
+ unsigned int guest_irq)
+{
+ irq_hw_number_t gic_irq;
+ struct irq_desc *desc = irq_to_desc(host_irq);
+ struct irq_data *d;
+ unsigned long flags;
+ struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, 0);
+ int ret = 0;
+ int spi_id = guest_irq + VGIC_NR_PRIVATE_IRQS;
+ struct vgic_dist *dist = &kvm->arch.vgic;
+
+ if (!vcpu)
+ return 0;
+
+ spin_lock(&dist->lock);
+
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ d = &desc->irq_data;
+ gic_irq = irqd_to_hwirq(d);
+ irqd_set_irq_forwarded(d);
+ /*
+ * next physical IRQ will be be handled as forwarded
+ * by the host (priority drop only)
+ */
+
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+ /*
+ * need to release the dist spin_lock here since
+ * vgic_map_phys_irq can sleep
+ */
+ spin_unlock(&dist->lock);
+ ret = vgic_map_phys_irq(vcpu, spi_id, (int)gic_irq);
+ /*
+ * next guest_irq injection will be considered as
+ * forwarded and next flush will program LR
+ * without maintenance IRQ but with HW bit set
+ */
+ return ret;
+}
+
+/**
+ * kvm_arch_unset_forward - Unset forwarding for a given IRQ
+ *
+ * @kvm: handle to the VM
+ * @host_irq: physical IRQ number
+ * @guest_irq: virtual IRQ number
+ * @active: returns whether the physical IRQ is active
+ *
+ * This function must be called when the host_irq is disabled
+ * and guest has been exited and prevented from being re-entered.
+ *
+ */
+void kvm_arch_unset_forward(struct kvm *kvm,
+ unsigned int host_irq,
+ unsigned int guest_irq,
+ bool *active)
+{
+ struct kvm_vcpu *vcpu = kvm_get_vcpu(kvm, 0);
+ struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+ struct vgic_dist *dist = &kvm->arch.vgic;
+ int ret, lr;
+ struct vgic_lr vlr;
+ struct irq_desc *desc = irq_to_desc(host_irq);
+ struct irq_data *d;
+ unsigned long flags;
+ irq_hw_number_t gic_irq;
+ int spi_id = guest_irq + VGIC_NR_PRIVATE_IRQS;
+ struct irq_chip *chip;
+ bool queued, needs_deactivate = true;
+
+ spin_lock(&dist->lock);
+
+ irq_get_irqchip_state(host_irq, IRQCHIP_STATE_ACTIVE, active);
+
+ if (!vcpu)
+ goto out;
+
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ d = irq_desc_get_irq_data(desc);
+ gic_irq = irqd_to_hwirq(d);
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+ ret = vgic_unmap_phys_irq(vcpu, spi_id, gic_irq);
+ /*
+ * subsequent update_irq_pending or flush will handle this
+ * irq as forwarded
+ */
+
+ if (likely(!(*active))) {
+ /*
+ * the IRQ was not active. It may happen the handle_fasteoi_irq
+ * is entered afterwards due to lazy disable_irq. If this
+ * happens the IRQ will be deactivated and never be injected.
+ * let's simply prepare the states for subsequent non forwarded
+ * injection
+ */
+ vgic_dist_irq_clear_level(vcpu, spi_id);
+ vgic_dist_irq_clear_pending(vcpu, spi_id);
+ vgic_irq_clear_queued(vcpu, spi_id);
+ needs_deactivate = false;
+ goto out;
+ }
+
+ /* is there any list register with valid state? */
+ lr = vgic_cpu->vgic_irq_lr_map[spi_id];
+ queued = false;
+ if (lr != LR_EMPTY) {
+ vlr = vgic_get_lr(vcpu, lr);
+ if (vlr.state & LR_STATE_MASK)
+ queued = true;
+ }
+
+ if (!queued) {
+ vgic_irq_clear_queued(vcpu, spi_id);
+ if (vgic_dist_irq_is_pending(vcpu, spi_id)) {
+ /*
+ * IRQ is injected but not yet queued. LR will be
+ * written with EOI_INT and process_maintenance will
+ * reset the states: queued, level(resampler). Pending
+ * will be reset on flush.
+ */
+ vgic_dist_irq_set_level(vcpu, spi_id);
+ } else {
+ /*
+ * We are before the injection (update_irq_pending).
+ * This is the most tricky window. Due to the usage of
+ * disable_irq in generic unforward part (mandated by
+ * resamplefd unmask VFIO integration), there is a risk
+ * the fasteoi handler returns without calling the VFIO
+ * handler and deactivates the physical IRQ (lazy
+ * disable). Hence we cannot know whether the IRQ will
+ * ever be injected. The only solution found is to do as
+ * if the IRQ were not active. The active parameter
+ * typically is used by the caller to know whether
+ * it needs to mask * the IRQ. If not duly masked,
+ * another physical IRQ may hit again while the previous
+ * virtual IRQ is in progress. Update_irq_pending
+ * validate_injection will prevent this injection.
+ */
+ vgic_dist_irq_clear_level(vcpu, spi_id);
+ *active = false;
+ }
+ goto out;
+ }
+
+ /*
+ * the virtual IRQ is queued and a valid LR exists, let's patch it for
+ * EOI maintenance
+ */
+ vlr.state |= LR_EOI_INT;
+ vgic_set_lr(vcpu, lr, vlr);
+ /*
+ * we expect a maintenance IRQ which will reset the
+ * queued, pending and level states
+ */
+ vgic_dist_irq_set_level(vcpu, spi_id);
+ vgic_dist_irq_set_pending(vcpu, spi_id);
+ vgic_irq_set_queued(vcpu, spi_id);
+
+out:
+
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ d = irq_desc_get_irq_data(desc);
+ if (needs_deactivate) {
+ chip = irq_data_get_irq_chip(d);
+ chip->irq_eoi(d);
+ }
+ irqd_clr_irq_forwarded(d);
+ /* next occurrence will be deactivated by the host */
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+
+ *active = *active && vcpu;
+
+ spin_unlock(&dist->lock);
+}
+
--
1.9.1


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