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 | 11 +++
arch/x86/kvm/x86.c | 1
include/linux/kvm.h | 3 +
include/linux/kvm_host.h | 4 +
virt/kvm/eventfd.c | 128 +++++++++++++++++++++++++++++++++++--
5 files changed, 139 insertions(+), 8 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index bf33aaa..3911e62 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1936,7 +1936,7 @@ Capability: KVM_CAP_IRQFD
Architectures: x86
Type: vm ioctl
Parameters: struct kvm_irqfd (in)
-Returns: 0 on success, -1 on error
+Returns: 0 (or >= 0) on success, -1 on error
Allows setting an eventfd to directly trigger a guest interrupt.
kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
@@ -1946,6 +1946,15 @@ 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. The
+return value when called with this flag is a key (>= 0) which may be
+used to associate this irqfd with other ioctls. KVM_IRQFD_FLAG_LEVEL
+support is indicated by KVM_CAP_IRQFD_LEVEL.
+
4.76 KVM_PPC_ALLOCATE_HTAB
Capability: KVM_CAP_PPC_ALLOC_HTAB
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 59b5950..9ded39d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2170,6 +2170,7 @@ 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/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b70b48b..c73f071 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -285,6 +285,10 @@ struct kvm {
struct list_head items;
} irqfds;
struct list_head ioeventfds;
+ struct {
+ struct mutex lock;
+ struct list_head items;
+ } irqsources;
#endif
struct kvm_vm_stat stat;
struct kvm_arch arch;
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 7d7e2aa..878cb52 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -36,6 +36,66 @@
#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 */
+ int gsi;
+ struct kvm *kvm;
+ struct list_head list;
+ struct kref kref;
+};
+
+static void _irq_source_release(struct kref *kref)
+{
+ struct _irq_source *source =
+ container_of(kref, struct _irq_source, kref);
+
+ /* This also de-asserts */
+ kvm_free_irq_source_id(source->kvm, source->id);
+ list_del(&source->list);
+ kfree(source);
+}
+
+static void _irq_source_put(struct _irq_source *source)
+{
+ if (source) {
+ mutex_lock(&source->kvm->irqsources.lock);
+ kref_put(&source->kref, _irq_source_release);
+ mutex_unlock(&source->kvm->irqsources.lock);
+ }
+}
+
+static struct _irq_source *_irq_source_alloc(struct kvm *kvm, int gsi)
+{
+ 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);
+ source->kvm = kvm;
+ source->id = id;
+ source->gsi = gsi;
+
+ mutex_lock(&kvm->irqsources.lock);
+ list_add_tail(&source->list, &kvm->irqsources.items);
+ mutex_unlock(&kvm->irqsources.lock);
+
+ return source;
+}
+
+/*
* --------------------------------------------------------------------
* irqfd: Allows an fd to be used to inject an interrupt to the guest
*
@@ -52,6 +112,8 @@ 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 +124,7 @@ 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 +133,22 @@ 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);
+
+ /*
+ * 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.
+ */
+ kvm_set_irq(irqfd->kvm, irqfd->source->id, irqfd->gsi, 1);
+}
+
/*
* Race-free decouple logic (ordering is critical)
*/
@@ -96,6 +174,9 @@ 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);
}
@@ -202,9 +283,10 @@ 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;
+ int ret = 0;
unsigned int events;
irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
@@ -214,7 +296,35 @@ 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) {
+ bool first = true;
+retry:
+ source = _irq_source_alloc(kvm, args->gsi);
+ if (IS_ERR(source)) {
+ /*
+ * If the irqfd is released we queue the cleanup
+ * wq but don't flush it. This could mean there's
+ * an irq source id waiting to be released. flush
+ * here and make another attempt.
+ */
+ if (first) {
+ flush_workqueue(irqfd_cleanup_wq);
+ first = false;
+ goto retry;
+ }
+ ret = PTR_ERR(source);
+ goto fail;
+ }
+
+ irqfd->source = source;
+ INIT_WORK(&irqfd->inject, irqfd_inject_level);
+
+ /* On success, return the irq source ID as a "key" */
+ ret = source->id;
+ } else
+ INIT_WORK(&irqfd->inject, irqfd_inject_edge);
+
INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
file = eventfd_fget(args->fd);
@@ -240,7 +350,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
spin_lock_irq(&kvm->irqfds.lock);
- ret = 0;
list_for_each_entry(tmp, &kvm->irqfds.items, list) {
if (irqfd->eventfd != tmp->eventfd)
continue;
@@ -273,13 +382,16 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
*/
fput(file);
- return 0;
+ return ret;
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);
@@ -292,6 +404,8 @@ kvm_eventfd_init(struct kvm *kvm)
spin_lock_init(&kvm->irqfds.lock);
INIT_LIST_HEAD(&kvm->irqfds.items);
INIT_LIST_HEAD(&kvm->ioeventfds);
+ mutex_init(&kvm->irqsources.lock);
+ INIT_LIST_HEAD(&kvm->irqsources.items);
}
/*
@@ -340,7 +454,7 @@ 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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