[PATCH v6 10/15] KVM: arm64: connect LPIs to the VGIC emulation
Andre Przywara
andre.przywara at arm.com
Fri Jun 17 05:08:42 PDT 2016
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 an RCU protected list to hold all mapped LPIs. vgic_its_get_lpi()
iterates the list using RCU list primitives, so it's safe to be called
from an non-preemptible context like the KVM exit/entry path.
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_its_get_lpi() from vgic_get_irq(), so
the VGIC code gets transparently access to LPIs.
Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
include/kvm/vgic/vgic.h | 5 +++
virt/kvm/arm/vgic/vgic-init.c | 3 ++
virt/kvm/arm/vgic/vgic-its.c | 92 ++++++++++++++++++++++++++++++++++++++++++-
virt/kvm/arm/vgic/vgic-v3.c | 2 +
virt/kvm/arm/vgic/vgic.c | 9 +++--
virt/kvm/arm/vgic/vgic.h | 6 +++
6 files changed, 111 insertions(+), 6 deletions(-)
diff --git a/include/kvm/vgic/vgic.h b/include/kvm/vgic/vgic.h
index 891775e..fdc2781 100644
--- a/include/kvm/vgic/vgic.h
+++ b/include/kvm/vgic/vgic.h
@@ -77,6 +77,8 @@ enum vgic_irq_config {
struct vgic_irq {
spinlock_t irq_lock; /* Protects the content of the struct */
+ struct list_head lpi_entry; /* Used to link all LPIs together */
+ struct rcu_head rcu;
struct list_head ap_list;
struct kvm_vcpu *vcpu; /* SGIs and PPIs: The VCPU
@@ -181,6 +183,9 @@ struct vgic_dist {
* GICv3 spec: 6.1.2 "LPI Configuration tables"
*/
u64 propbaser;
+
+ struct list_head lpi_list_head;
+ struct mutex lpi_list_lock;
};
struct vgic_v2_cpu_if {
diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index c4a8df6..d22b094 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);
+ mutex_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 d7f8834..9ef951f7 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -22,6 +22,7 @@
#include <linux/kvm_host.h>
#include <linux/interrupt.h>
#include <linux/list.h>
+#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/irqchip/arm-gic-v3.h>
@@ -33,6 +34,85 @@
#include "vgic.h"
#include "vgic-mmio.h"
+/*
+ * Iterate over the VM's list of mapped LPIs to find the one with a
+ * matching INTID, _lock that_ and return a pointer to the IRQ structure.
+ * Although the corresponding LPI could be unmapped (removed from the ITS
+ * data structures) even when someone holds the IRQ lock, the reference to
+ * this struct vgic_irq stays valid within the VGIC context at least until
+ * the lock gets dropped.
+ */
+struct vgic_irq *vgic_its_get_lpi(struct kvm *kvm, u32 intid)
+{
+ struct vgic_dist *dist = &kvm->arch.vgic;
+ struct vgic_irq *irq = NULL;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(irq, &dist->lpi_list_head, lpi_entry) {
+ if (irq->intid != intid)
+ continue;
+
+ spin_lock(&irq->irq_lock);
+ goto out_unlock;
+ }
+ irq = NULL;
+
+out_unlock:
+ rcu_read_unlock();
+
+ return irq;
+}
+
+static void vgic_free_irq_rcu(struct rcu_head *head)
+{
+ struct vgic_irq *irq = container_of(head, struct vgic_irq, rcu);
+
+ kfree(irq);
+}
+
+/*
+ * Drops a reference to an LPI. This is called whenever one ITS unmaps
+ * the LPI: it decreases the refcount and frees the structure if the
+ * refcount has reached zero.
+ * If this LPI is still referenced by another LPI and is on a VCPU at the
+ * moment, the removal will be deferred until those references go away as well.
+ */
+int vgic_drop_lpi(struct kvm *kvm, u32 intid)
+{
+ struct vgic_dist *dist = &kvm->arch.vgic;
+ struct vgic_irq *irq, *temp;
+
+ mutex_lock(&dist->lpi_list_lock);
+ list_for_each_entry_safe(irq, temp, &dist->lpi_list_head, lpi_entry) {
+ if (irq->intid != intid)
+ continue;
+
+ spin_lock(&irq->irq_lock);
+
+ irq->refcnt--;
+ if (!irq->refcnt) {
+ list_del_rcu(&irq->lpi_entry);
+ spin_unlock(&irq->irq_lock);
+ call_rcu(&irq->rcu, vgic_free_irq_rcu);
+ } else {
+ /*
+ * If the refcnt is not zero here, this could be due to
+ * two cases:
+ * 1) it's referenced by another ITS: then the last ITS
+ * will free the IRQ once it is done with it
+ * 2) it's on a VCPU at the moment: upon returning from
+ * the guest vgic_prune_ap_list() will free the IRQ
+ */
+ spin_unlock(&irq->irq_lock);
+ }
+ break;
+ }
+
+ mutex_unlock(&dist->lpi_list_lock);
+
+ return 0;
+}
+
struct its_device {
struct list_head dev_list;
@@ -56,11 +136,17 @@ struct its_collection {
struct its_itte {
struct list_head itte_list;
+ struct vgic_irq *irq;
struct its_collection *collection;
u32 lpi;
u32 event_id;
};
+/* To be used as an iterator this macro misses the enclosing parentheses */
+#define for_each_lpi_its(dev, itte, its) \
+ list_for_each_entry(dev, &(its)->device_list, dev_list) \
+ list_for_each_entry(itte, &(dev)->itt_head, itte_list)
+
#define CBASER_ADDRESS(x) ((x) & GENMASK_ULL(51, 12))
#define BASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 12))
@@ -148,9 +234,11 @@ static unsigned long vgic_mmio_read_its_idregs(struct kvm *kvm,
return 0;
}
-static void its_free_itte(struct its_itte *itte)
+static void its_free_itte(struct kvm *kvm, struct its_itte *itte)
{
list_del(&itte->itte_list);
+ vgic_drop_lpi(kvm, itte->lpi);
+
kfree(itte);
}
@@ -404,7 +492,7 @@ static void vits_destroy(struct kvm *kvm, struct vgic_its *its)
dev = container_of(dev_cur, struct its_device, dev_list);
list_for_each_safe(cur, temp, &dev->itt_head) {
itte = (container_of(cur, struct its_itte, itte_list));
- its_free_itte(itte);
+ its_free_itte(kvm, itte);
}
list_del(dev_cur);
kfree(dev);
diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
index 21d84e9..74ab7a6 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;
/* Always preserve the active bit */
irq->active = !!(val & ICH_LR_ACTIVE_BIT);
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index 90f2543..4655ae4 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -63,12 +63,13 @@ struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
return irq;
}
- /* LPIs are not yet covered */
- if (intid >= VGIC_MIN_LPI)
+ if (intid < VGIC_MIN_LPI) {
+ WARN(1, "Looking up struct vgic_irq for reserved INTID");
return NULL;
+ }
- WARN(1, "Looking up struct vgic_irq for reserved INTID");
- return NULL;
+ /* LPIs */
+ return vgic_its_get_lpi(kvm, intid);
}
/**
diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
index 24150f7..558252d 100644
--- a/virt/kvm/arm/vgic/vgic.h
+++ b/virt/kvm/arm/vgic/vgic.h
@@ -81,6 +81,7 @@ int vgic_v3_map_resources(struct kvm *kvm);
int vgic_register_redist_iodevs(struct kvm *kvm, gpa_t dist_base_address);
bool vgic_has_its(struct kvm *kvm);
int kvm_vgic_register_its_device(void);
+struct vgic_irq *vgic_its_get_lpi(struct kvm *kvm, u32 intid);
#else
static inline void vgic_v3_process_maintenance(struct kvm_vcpu *vcpu)
{
@@ -142,6 +143,11 @@ static inline int kvm_vgic_register_its_device(void)
{
return -ENODEV;
}
+
+static inline struct vgic_irq *vgic_its_get_lpi(struct kvm *kvm, u32 intid)
+{
+ return NULL;
+}
#endif
int kvm_register_vgic_device(unsigned long type);
--
2.8.2
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