[PATCH 37/55] KVM: arm64: vgic-its: Connect LPIs to the VGIC emulation

Marc Zyngier
2016-07-22T17:28:54Z

From: Andre Przywara <andre.przywara@arm.com>

LPIs are dynamically created (mapped) at guest runtime and their
actual number can be quite high, but is mostly assigned using a very
sparse allocation scheme. So arrays are not an ideal data structure
to hold the information.
We use a spin-lock protected linked list to hold all mapped LPIs,
represented by their struct vgic_irq. This lock is grouped between the
ap_list_lock and the vgic_irq lock in our locking order.
Also we store a pointer to that struct vgic_irq in our struct its_itte,
so we can easily access it.
Eventually we call our new vgic_get_lpi() from vgic_get_irq(), so
the VGIC code gets transparently access to LPIs.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
include/kvm/arm_vgic.h | 6 +++++
virt/kvm/arm/vgic/vgic-init.c | 3 +++
virt/kvm/arm/vgic/vgic-its.c | 5 ++++
virt/kvm/arm/vgic/vgic-v3.c | 2 ++
virt/kvm/arm/vgic/vgic.c | 63 ++++++++++++++++++++++++++++++++++++++-----
5 files changed, 73 insertions(+), 6 deletions(-)

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 6186749..a6ca326 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -77,6 +77,7 @@ enum vgic_irq_config {

struct vgic_irq {
spinlock_t irq_lock; /* Protects the content of the struct */
+ struct list_head lpi_list; /* Used to link all LPIs together */
struct list_head ap_list;

struct kvm_vcpu *vcpu; /* SGIs and PPIs: The VCPU
@@ -193,6 +194,11 @@ struct vgic_dist {
* GICv3 spec: 6.1.2 "LPI Configuration tables"
*/
u64 propbaser;
+
+ /* Protects the lpi_list and the count value below. */
+ spinlock_t lpi_list_lock;
+ struct list_head lpi_list_head;
+ int lpi_list_count;
};

struct vgic_v2_cpu_if {
diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index ac3c1a5..535e713 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -157,6 +157,9 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
struct kvm_vcpu *vcpu0 = kvm_get_vcpu(kvm, 0);
int i;

+ INIT_LIST_HEAD(&dist->lpi_list_head);
+ spin_lock_init(&dist->lpi_list_lock);
+
dist->spis = kcalloc(nr_spis, sizeof(struct vgic_irq), GFP_KERNEL);
if (!dist->spis)
return -ENOMEM;
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 11cfe2f..14f91ff 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -56,6 +56,7 @@ struct its_collection {
struct its_itte {
struct list_head itte_list;

+ struct vgic_irq *irq;
struct its_collection *collection;
u32 lpi;
u32 event_id;
@@ -148,6 +149,10 @@ static unsigned long vgic_mmio_read_its_idregs(struct kvm *kvm,
static void its_free_itte(struct kvm *kvm, struct its_itte *itte)
{
list_del(&itte->itte_list);
+
+ /* This put matches the get in vgic_add_lpi. */
+ vgic_put_irq(kvm, itte->irq);
+
kfree(itte);
}

diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 6f8f31f..0506543 100644
--- a/virt/kvm/arm/vgic/vgic-v3.c
+++ b/virt/kvm/arm/vgic/vgic-v3.c
@@ -81,6 +81,8 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu)
else
intid = val & GICH_LR_VIRTUALID;
irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
+ if (!irq) /* An LPI could have been unmapped. */
+ continue;

spin_lock(&irq->irq_lock);

diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index d3ba1b4..53299fc 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -36,7 +36,8 @@ struct vgic_global __section(.hyp.text) kvm_vgic_global_state;
* its->cmd_lock (mutex)
* its->its_lock (mutex)
* vgic_cpu->ap_list_lock
- * vgic_irq->irq_lock
+ * kvm->lpi_list_lock
+ * vgic_irq->irq_lock
*
* If you need to take multiple locks, always take the upper lock first,
* then the lower ones, e.g. first take the its_lock, then the irq_lock.
@@ -51,6 +52,41 @@ struct vgic_global __section(.hyp.text) kvm_vgic_global_state;
* spin_lock(vcpuY->arch.vgic_cpu.ap_list_lock);
*/

+/*
+ * Iterate over the VM's list of mapped LPIs to find the one with a
+ * matching interrupt ID and return a reference to the IRQ structure.
+ */
+static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
+{
+ struct vgic_dist *dist = &kvm->arch.vgic;
+ struct vgic_irq *irq = NULL;
+
+ spin_lock(&dist->lpi_list_lock);
+
+ list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
+ if (irq->intid != intid)
+ continue;
+
+ /*
+ * This increases the refcount, the caller is expected to
+ * call vgic_put_irq() later once it's finished with the IRQ.
+ */
+ kref_get(&irq->refcount);
+ goto out_unlock;
+ }
+ irq = NULL;
+
+out_unlock:
+ spin_unlock(&dist->lpi_list_lock);
+
+ return irq;
+}
+
+/*
+ * This looks up the virtual interrupt ID to get the corresponding
+ * struct vgic_irq. It also increases the refcount, so any caller is expected
+ * to call vgic_put_irq() once it's finished with this IRQ.
+ */
struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
u32 intid)
{
@@ -62,9 +98,9 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
if (intid <= VGIC_MAX_SPI)
return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];

- /* LPIs are not yet covered */
+ /* LPIs */
if (intid >= VGIC_MIN_LPI)
- return NULL;
+ return vgic_get_lpi(kvm, intid);

WARN(1, "Looking up struct vgic_irq for reserved INTID");
return NULL;
@@ -78,18 +114,33 @@ static void vgic_get_irq_kref(struct vgic_irq *irq)
kref_get(&irq->refcount);
}

-/* The refcount should never drop to 0 at the moment. */
+/*
+ * We can't do anything in here, because we lack the kvm pointer to
+ * lock and remove the item from the lpi_list. So we keep this function
+ * empty and use the return value of kref_put() to trigger the freeing.
+ */
static void vgic_irq_release(struct kref *ref)
{
- WARN_ON(1);
}

void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
{
+ struct vgic_dist *dist;
+
if (irq->intid < VGIC_MIN_LPI)
return;

- kref_put(&irq->refcount, vgic_irq_release);
+ if (!kref_put(&irq->refcount, vgic_irq_release))
+ return;
+
+ dist = &kvm->arch.vgic;
+
+ spin_lock(&dist->lpi_list_lock);
+ list_del(&irq->lpi_list);
+ dist->lpi_list_count--;
+ spin_unlock(&dist->lpi_list_lock);
+
+ kfree(irq);
}

/**
--
2.8.1