On Tue, Jun 26, 2012 at 11:09:46PM -0600, Alex Williamson wrote:
> In order to inject an 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 | 5 ++
> arch/x86/kvm/x86.c | 1
> include/linux/kvm.h | 3 +
> virt/kvm/eventfd.c | 95 +++++++++++++++++++++++++++++++++++--
> 4 files changed, 99 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index ea9edce..b216709 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1981,6 +1981,11 @@ 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.
>
> +With KVM_IRQFD_FLAG_LEVEL KVM_IRQFD allocates a new IRQ source ID for
> +the requested irqfd. This is necessary to share level triggered
> +interrupts with those injected through KVM_IRQ_LINE. IRQFDs created
> +with KVM_IRQFD_FLAG_LEVEL must also set this flag when de-assiging.
> +KVM_IRQFD_FLAG_LEVEL support is indicated by KVM_CAP_IRQFD_LEVEL.
Note that if my patch removing auto-deassert gets accepted,
this is not needed at all: we can just look at the GSI
to see if it's level or edge.
>
> 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..18cc284 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -36,6 +36,64 @@
> #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;
> + struct kvm *kvm;
> + struct kref kref;
> +};
> +
> +static void release_irq_source(struct kref *kref)
> +{
> + struct _irq_source *source;
> +
> + source = container_of(kref, struct _irq_source, kref);
> +
> + kvm_free_irq_source_id(source->kvm, source->id);
> + kfree(source);
> +}
> +
> +static void put_irq_source(struct _irq_source *source)
> +{
> + if (source)
> + kref_put(&source->kref, release_irq_source);
> +}
> +
> +static struct _irq_source *__attribute__ ((used)) /* white lie for now */
> +get_irq_source(struct _irq_source *source)
> +{
> + if (source)
> + kref_get(&source->kref);
> +
> + return source;
> +}
> +
> +static struct _irq_source *new_irq_source(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);
> + source->kvm = kvm;
> + source->id = id;
> +
> + return source;
> +}
> +
> +/*
> * --------------------------------------------------------------------
> * irqfd: Allows an fd to be used to inject an interrupt to the guest
> *
> @@ -52,6 +110,7 @@ struct _irqfd {
> /* Used for level IRQ fast-path */
> int gsi;
> struct work_struct inject;
> + struct _irq_source *source;
> /* Used for setup/shutdown */
> struct eventfd_ctx *eventfd;
> struct list_head list;
> @@ -62,7 +121,7 @@ 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 +130,14 @@ 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);
> +
> + kvm_set_irq(irqfd->kvm, irqfd->source->id, irqfd->gsi, 1);
> +}
> +
> /*
> * Race-free decouple logic (ordering is critical)
> */
> @@ -96,6 +163,9 @@ irqfd_shutdown(struct work_struct *work)
> * It is now safe to release the object's resources
> */
> eventfd_ctx_put(irqfd->eventfd);
> +
> + put_irq_source(irqfd->source);
> +
> kfree(irqfd);
> }
>
> @@ -214,7 +284,19 @@ 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) {
> + irqfd->source = new_irq_source(kvm);
> + if (IS_ERR(irqfd->source)) {
> + ret = PTR_ERR(irqfd->source);
> + irqfd->source = NULL;
> + goto fail;
> + }
> +
> + 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);
> @@ -279,9 +361,10 @@ fail:
> if (eventfd && !IS_ERR(eventfd))
> eventfd_ctx_put(eventfd);
>
> - if (!IS_ERR(file))
> + if (file && !IS_ERR(file))
> fput(file);
>
> + put_irq_source(irqfd->source);
> kfree(irqfd);
> return ret;
> }
> @@ -302,6 +385,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
> {
> struct _irqfd *irqfd, *tmp;
> struct eventfd_ctx *eventfd;
> + bool is_level = (args->flags & KVM_IRQFD_FLAG_LEVEL) != 0;
>
> eventfd = eventfd_ctx_fdget(args->fd);
> if (IS_ERR(eventfd))
> @@ -310,7 +394,8 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
> spin_lock_irq(&kvm->irqfds.lock);
>
> list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
> - if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
> + if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi &&
> + is_level == (irqfd->source != NULL)) {
> /*
> * This rcu_assign_pointer is needed for when
> * another thread calls kvm_irq_routing_update before
> @@ -340,7 +425,7 @@ 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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