In order to inject a level interrupt from an external source using an
irqfd, we need to allocate a new irq_source_id. This allows us to
assert and (later) de-assert an interrupt line independently from
users of KVM_IRQ_LINE and avoid lost interrupts.
We also add what may appear like a bit of excessive infrastructure
around an object for storing this irq_source_id. However, notice
that we only provide a way to assert the interrupt here. A follow-on
interface will make use of the same irq_source_id to allow de-assert.
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
---
Documentation/virtual/kvm/api.txt | 6 ++
arch/x86/kvm/x86.c | 1
include/linux/kvm.h | 3 +
virt/kvm/eventfd.c | 114 ++++++++++++++++++++++++++++++++++++-
4 files changed, 120 insertions(+), 4 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 100acde..c7267d5 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1981,6 +1981,12 @@ the guest using the specified gsi pin. The irqfd is removed using
the KVM_IRQFD_FLAG_DEASSIGN flag, specifying both kvm_irqfd.fd
and kvm_irqfd.gsi.
+The KVM_IRQFD_FLAG_LEVEL flag indicates the gsi input is for a level
+triggered interrupt. In this case a new irqchip input is allocated
+which is logically OR'd with other inputs allowing multiple sources
+to independently assert level interrupts. The KVM_IRQFD_FLAG_LEVEL
+is only necessary on setup, teardown is identical to that above.
+KVM_IRQFD_FLAG_LEVEL support is indicated by KVM_CAP_IRQFD_LEVEL.
5. The kvm_run structure
------------------------
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a01a424..80bed07 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2148,6 +2148,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_GET_TSC_KHZ:
case KVM_CAP_PCI_2_3:
case KVM_CAP_KVMCLOCK_CTRL:
+ case KVM_CAP_IRQFD_LEVEL:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 2ce09aa..b2e6e4f 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -618,6 +618,7 @@ struct kvm_ppc_smmu_info {
#define KVM_CAP_PPC_GET_SMMU_INFO 78
#define KVM_CAP_S390_COW 79
#define KVM_CAP_PPC_ALLOC_HTAB 80
+#define KVM_CAP_IRQFD_LEVEL 81
#ifdef KVM_CAP_IRQ_ROUTING
@@ -683,6 +684,8 @@ struct kvm_xen_hvm_config {
#endif
#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
+/* Available with KVM_CAP_IRQFD_LEVEL */
+#define KVM_IRQFD_FLAG_LEVEL (1 << 1)
struct kvm_irqfd {
__u32 fd;
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 7d7e2aa..ecdbfea 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -36,6 +36,68 @@
#include "iodev.h"
/*
+ * An irq_source_id can be created from KVM_IRQFD for level interrupt
+ * injections and shared with other interfaces for EOI or de-assert.
+ * Create an object with reference counting to make it easy to use.
+ */
+struct _irq_source {
+ int id; /* the IRQ source ID */
+ bool level_asserted; /* Track assertion state and protect with lock */
+ spinlock_t lock; /* to avoid unnecessary re-assert/spurious eoi. */
+ struct kvm *kvm;
+ struct kref kref;
+};
+
+static void _irq_source_release(struct kref *kref)
+{
+ struct _irq_source *source;
+
+ source = container_of(kref, struct _irq_source, kref);
+
+ /* This also de-asserts */
+ kvm_free_irq_source_id(source->kvm, source->id);
+ kfree(source);
+}
+
+static void _irq_source_put(struct _irq_source *source)
+{
+ if (source)
+ kref_put(&source->kref, _irq_source_release);
+}
+
+static struct _irq_source *__attribute__ ((used)) /* white lie for now */
+_irq_source_get(struct _irq_source *source)
+{
+ if (source)
+ kref_get(&source->kref);
+
+ return source;
+}
+
+static struct _irq_source *_irq_source_alloc(struct kvm *kvm)
+{
+ struct _irq_source *source;
+ int id;
+
+ source = kzalloc(sizeof(*source), GFP_KERNEL);
+ if (!source)
+ return ERR_PTR(-ENOMEM);
+
+ id = kvm_request_irq_source_id(kvm);
+ if (id < 0) {
+ kfree(source);
+ return ERR_PTR(id);
+ }
+
+ kref_init(&source->kref);
+ spin_lock_init(&source->lock);
+ source->kvm = kvm;
+ source->id = id;
+
+ return source;
+}
+
+/*
* --------------------------------------------------------------------
* irqfd: Allows an fd to be used to inject an interrupt to the guest
*
@@ -52,6 +114,8 @@ struct _irqfd {
/* Used for level IRQ fast-path */
int gsi;
struct work_struct inject;
+ /* IRQ source ID for level triggered irqfds */
+ struct _irq_source *source;
/* Used for setup/shutdown */
struct eventfd_ctx *eventfd;
struct list_head list;
@@ -62,7 +126,7 @@ struct _irqfd {
static struct workqueue_struct *irqfd_cleanup_wq;
static void
-irqfd_inject(struct work_struct *work)
+irqfd_inject_edge(struct work_struct *work)
{
struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
struct kvm *kvm = irqfd->kvm;
@@ -71,6 +135,29 @@ irqfd_inject(struct work_struct *work)
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
}
+static void
+irqfd_inject_level(struct work_struct *work)
+{
+ struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
+
+ /*
+ * Inject an interrupt only if not already asserted.
+ *
+ * We can safely ignore the kvm_set_irq return value here. If
+ * masked, the irr bit is still set and will eventually be serviced.
+ * This interface does not guarantee immediate injection. If
+ * coalesced, an eoi will be coming where we can de-assert and
+ * re-inject if necessary. NB, if you need to know if an interrupt
+ * was coalesced, this interface is not for you.
+ */
+ spin_lock(&irqfd->source->lock);
+ if (!irqfd->source->level_asserted) {
+ kvm_set_irq(irqfd->kvm, irqfd->source->id, irqfd->gsi, 1);
+ irqfd->source->level_asserted = true;
+ }
+ spin_unlock(&irqfd->source->lock);
+}
+
/*
* Race-free decouple logic (ordering is critical)
*/
@@ -96,6 +183,9 @@ irqfd_shutdown(struct work_struct *work)
* It is now safe to release the object's resources
*/
eventfd_ctx_put(irqfd->eventfd);
+
+ _irq_source_put(irqfd->source);
+
kfree(irqfd);
}
@@ -202,6 +292,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
{
struct kvm_irq_routing_table *irq_rt;
struct _irqfd *irqfd, *tmp;
+ struct _irq_source *source = NULL;
struct file *file = NULL;
struct eventfd_ctx *eventfd = NULL;
int ret;
@@ -214,7 +305,19 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
irqfd->kvm = kvm;
irqfd->gsi = args->gsi;
INIT_LIST_HEAD(&irqfd->list);
- INIT_WORK(&irqfd->inject, irqfd_inject);
+
+ if (args->flags & KVM_IRQFD_FLAG_LEVEL) {
+ source = _irq_source_alloc(kvm);
+ if (IS_ERR(source)) {
+ ret = PTR_ERR(source);
+ goto fail;
+ }
+
+ irqfd->source = source;
+ INIT_WORK(&irqfd->inject, irqfd_inject_level);
+ } else
+ INIT_WORK(&irqfd->inject, irqfd_inject_edge);
+
INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
file = eventfd_fget(args->fd);
@@ -276,10 +379,13 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
return 0;
fail:
+ if (source && !IS_ERR(source))
+ _irq_source_put(source);
+
if (eventfd && !IS_ERR(eventfd))
eventfd_ctx_put(eventfd);
- if (!IS_ERR(file))
+ if (file && !IS_ERR(file))
fput(file);
kfree(irqfd);
@@ -340,7 +446,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
int
kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
{
- if (args->flags & ~KVM_IRQFD_FLAG_DEASSIGN)
+ if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_LEVEL))
return -EINVAL;
if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
--
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