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Date: Sun, 15 Jul 2012 19:23:44 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: avi@...hat.com, gleb@...hat.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, jan.kiszka@...mens.com
Subject: Re: [PATCH v4 2/3] kvm: KVM_EOIFD, an eventfd for EOIs
On Fri, Jul 13, 2012 at 01:41:05PM -0600, Alex Williamson wrote:
> This new ioctl enables an eventfd to be triggered when an EOI is
> written for a specified irqchip pin. The first user of this will
> be external device assignment through VFIO, using a level irqfd
> for asserting a PCI INTx interrupt and this interface for de-assert
> and notification once the interrupt is serviced.
>
> Here we make use of the reference counting of the _irq_source
> object allowing us to share it with an irqfd and cleanup regardless
> of the release order.
>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>
> Documentation/virtual/kvm/api.txt | 21 +++
> arch/x86/kvm/x86.c | 2
> include/linux/kvm.h | 15 ++
> include/linux/kvm_host.h | 13 ++
> virt/kvm/eventfd.c | 226 +++++++++++++++++++++++++++++++++++++
> virt/kvm/kvm_main.c | 11 ++
> 6 files changed, 286 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index c7267d5..d5be635 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -1988,6 +1988,27 @@ 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.
>
> +4.77 KVM_EOIFD
> +
> +Capability: KVM_CAP_EOIFD
> +Architectures: x86
> +Type: vm ioctl
> +Parameters: struct kvm_eoifd (in)
> +Returns: 0 on success, -1 on error
> +
> +KVM_EOIFD allows userspace to receive interrupt EOI notification
> +through an eventfd. kvm_eoifd.fd specifies the eventfd used for
> +notification. KVM_EOIFD_FLAG_DEASSIGN is used to de-assign an eoifd
> +once assigned. KVM_EOIFD also requires additional bits set in
> +kvm_eoifd.flags to bind to the proper interrupt line. The
> +KVM_EOIFD_FLAG_LEVEL_IRQFD indicates that kvm_eoifd.irqfd is provided
> +and is an irqfd for a level triggered interrupt (configured from
> +KVM_IRQFD using KVM_IRQFD_FLAG_LEVEL). The EOI notification is bound
> +to the same GSI and irqchip input as the irqfd. Both kvm_eoifd.irqfd
> +and KVM_EOIFD_FLAG_LEVEL_IRQFD must be specified both on assignment
> +and de-assignment of KVM_EOIFD. KVM_CAP_EOIFD_LEVEL_IRQFD indicates
> +support of KVM_EOIFD_FLAG_LEVEL_IRQFD.
> +
> 5. The kvm_run structure
> ------------------------
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 80bed07..cc47e31 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2149,6 +2149,8 @@ int kvm_dev_ioctl_check_extension(long ext)
> case KVM_CAP_PCI_2_3:
> case KVM_CAP_KVMCLOCK_CTRL:
> case KVM_CAP_IRQFD_LEVEL:
> + case KVM_CAP_EOIFD:
> + case KVM_CAP_EOIFD_LEVEL_IRQFD:
> r = 1;
> break;
> case KVM_CAP_COALESCED_MMIO:
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index b2e6e4f..5ca887d 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -619,6 +619,8 @@ struct kvm_ppc_smmu_info {
> #define KVM_CAP_S390_COW 79
> #define KVM_CAP_PPC_ALLOC_HTAB 80
> #define KVM_CAP_IRQFD_LEVEL 81
> +#define KVM_CAP_EOIFD 82
> +#define KVM_CAP_EOIFD_LEVEL_IRQFD 83
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> @@ -694,6 +696,17 @@ struct kvm_irqfd {
> __u8 pad[20];
> };
>
> +#define KVM_EOIFD_FLAG_DEASSIGN (1 << 0)
> +/* Available with KVM_CAP_EOIFD_LEVEL_IRQFD */
> +#define KVM_EOIFD_FLAG_LEVEL_IRQFD (1 << 1)
> +
> +struct kvm_eoifd {
> + __u32 fd;
> + __u32 flags;
> + __u32 irqfd;
> + __u8 pad[20];
> +};
> +
> struct kvm_clock_data {
> __u64 clock;
> __u32 flags;
> @@ -834,6 +847,8 @@ struct kvm_s390_ucas_mapping {
> #define KVM_PPC_GET_SMMU_INFO _IOR(KVMIO, 0xa6, struct kvm_ppc_smmu_info)
> /* Available with KVM_CAP_PPC_ALLOC_HTAB */
> #define KVM_PPC_ALLOCATE_HTAB _IOWR(KVMIO, 0xa7, __u32)
> +/* Available with KVM_CAP_EOIFD */
> +#define KVM_EOIFD _IOW(KVMIO, 0xa8, struct kvm_eoifd)
>
> /*
> * ioctls for vcpu fds
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index ae3b426..a7661c0 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;
> + } eoifds;
> #endif
> struct kvm_vm_stat stat;
> struct kvm_arch arch;
> @@ -828,6 +832,8 @@ int kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args);
> void kvm_irqfd_release(struct kvm *kvm);
> void kvm_irq_routing_update(struct kvm *, struct kvm_irq_routing_table *);
> int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args);
> +int kvm_eoifd(struct kvm *kvm, struct kvm_eoifd *args);
> +void kvm_eoifd_release(struct kvm *kvm);
>
> #else
>
> @@ -853,6 +859,13 @@ static inline int kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
> return -ENOSYS;
> }
>
> +static inline int kvm_eoifd(struct kvm *kvm, struct kvm_eoifd *args)
> +{
> + return -ENOSYS;
> +}
> +
> +static inline void kvm_eoifd_release(struct kvm *kvm) {}
> +
> #endif /* CONFIG_HAVE_KVM_EVENTFD */
>
> #ifdef CONFIG_KVM_APIC_ARCHITECTURE
> diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> index ecdbfea..2fae198 100644
> --- a/virt/kvm/eventfd.c
> +++ b/virt/kvm/eventfd.c
> @@ -65,8 +65,7 @@ static void _irq_source_put(struct _irq_source *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)
> +static struct _irq_source *_irq_source_get(struct _irq_source *source)
> {
> if (source)
> kref_get(&source->kref);
> @@ -123,6 +122,39 @@ struct _irqfd {
> struct work_struct shutdown;
> };
>
> +static struct _irqfd *_irqfd_fdget_lock(struct kvm *kvm, int fd)
> +{
> + struct eventfd_ctx *eventfd;
> + struct _irqfd *tmp, *irqfd = NULL;
> +
> + eventfd = eventfd_ctx_fdget(fd);
> + if (IS_ERR(eventfd))
> + return (struct _irqfd *)eventfd;
> +
> + spin_lock_irq(&kvm->irqfds.lock);
> +
> + list_for_each_entry(tmp, &kvm->irqfds.items, list) {
> + if (tmp->eventfd == eventfd) {
> + irqfd = tmp;
> + break;
> + }
> + }
> +
> + if (!irqfd) {
> + spin_unlock_irq(&kvm->irqfds.lock);
> + eventfd_ctx_put(eventfd);
> + return ERR_PTR(-ENODEV);
> + }
> +
> + return irqfd;
> +}
> +
> +static void _irqfd_put_unlock(struct _irqfd *irqfd)
> +{
> + eventfd_ctx_put(irqfd->eventfd);
> + spin_unlock_irq(&irqfd->kvm->irqfds.lock);
> +}
> +
> static struct workqueue_struct *irqfd_cleanup_wq;
>
> static void
> @@ -398,6 +430,8 @@ 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->eoifds.lock);
> + INIT_LIST_HEAD(&kvm->eoifds.items);
> }
>
> /*
> @@ -764,3 +798,191 @@ kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
>
> return kvm_assign_ioeventfd(kvm, args);
> }
> +
> +/*
> + * --------------------------------------------------------------------
> + * eoifd: Translate KVM APIC/IOAPIC EOI into eventfd signal.
> + *
> + * userspace can register with an eventfd for receiving
> + * notification when an EOI occurs.
> + * --------------------------------------------------------------------
> + */
> +
> +struct _eoifd {
> + /* eventfd triggered on EOI */
> + struct eventfd_ctx *eventfd;
> + /* irq source ID de-asserted on EOI */
> + struct _irq_source *source;
> + struct kvm *kvm;
> + struct kvm_irq_ack_notifier notifier;
> + /* reference to irqfd eventfd for de-assign matching */
> + struct eventfd_ctx *level_irqfd;
> + struct list_head list;
> +};
> +
> +static void eoifd_event(struct kvm_irq_ack_notifier *notifier)
> +{
> + struct _eoifd *eoifd;
> +
> + eoifd = container_of(notifier, struct _eoifd, notifier);
> +
> + /*
> + * Ack notifier is per GSI, which may be shared with others.
> + * Only de-assert and send EOI if our source ID is asserted.
> + * User needs to re-assert if device still requires service.
> + */
> + spin_lock(&eoifd->source->lock);
> + if (eoifd->source->level_asserted) {
> + kvm_set_irq(eoifd->kvm,
> + eoifd->source->id, eoifd->notifier.gsi, 0);
How about we add "clear" pic callback, in addition to set, and implement
kvm_set_irq with kvm_clear_irq which returns current status?
This would avoid the need for level_asserted and for locks, won't it?
--
MST
--
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