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    Subject[PATCH v8 6/6] kvm: Add de-assert option to KVM_IRQ_ACKFD
    Date
    It's likely (vfio) that one of the reasons to watch for an IRQ ACK
    is to de-assert and re-enable an interrupt. As the IRQ ACK notfier
    is already watching a GSI for an IRQ source ID we can easily couple
    these together.

    Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    ---

    Documentation/virtual/kvm/api.txt | 4 ++++
    arch/x86/kvm/x86.c | 1 +
    include/linux/kvm.h | 3 +++
    virt/kvm/eventfd.c | 14 +++++++++++++-
    4 files changed, 21 insertions(+), 1 deletion(-)

    diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
    index 77b4837..128d4c3 100644
    --- a/Documentation/virtual/kvm/api.txt
    +++ b/Documentation/virtual/kvm/api.txt
    @@ -2029,6 +2029,10 @@ the eventfd is only triggered when the specified IRQ source ID is
    pending. On deassign, fd, gsi, and irq_source_id (if provided on assign)
    must be provided.

    +When KVM_CAP_IRQ_ACKFD_DEASSERT is available the flag
    +KVM_IRQ_ACKFD_FLAG_IRQ_DEASSERT may be used on assignment to specify
    +that the GSI should be de-asserted prior to eventfd notification.
    +This flag requires an IRQ source ID to be provided as described above.

    5. The kvm_run structure
    ------------------------
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 3d98e59..691b00d 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -2178,6 +2178,7 @@ int kvm_dev_ioctl_check_extension(long ext)
    case KVM_CAP_IRQFD_ASSERT_ONLY:
    case KVM_CAP_IRQ_ACKFD:
    case KVM_CAP_IRQ_ACKFD_IRQ_SOURCE_ID:
    + case KVM_CAP_IRQ_ACKFD_DEASSERT:
    r = 1;
    break;
    case KVM_CAP_COALESCED_MMIO:
    diff --git a/include/linux/kvm.h b/include/linux/kvm.h
    index 0f53bd5..331631e 100644
    --- a/include/linux/kvm.h
    +++ b/include/linux/kvm.h
    @@ -623,6 +623,7 @@ struct kvm_ppc_smmu_info {
    #define KVM_CAP_IRQFD_ASSERT_ONLY 83
    #define KVM_CAP_IRQ_ACKFD 84
    #define KVM_CAP_IRQ_ACKFD_IRQ_SOURCE_ID 85
    +#define KVM_CAP_IRQ_ACKFD_DEASSERT 86

    #ifdef KVM_CAP_IRQ_ROUTING

    @@ -712,6 +713,8 @@ struct kvm_irq_source_id {
    #define KVM_IRQ_ACKFD_FLAG_DEASSIGN (1 << 0)
    /* Available with KVM_CAP_IRQ_ACKFD_IRQ_SOURCE_ID */
    #define KVM_IRQ_ACKFD_FLAG_IRQ_SOURCE_ID (1 << 1)
    +/* Available with KVM_CAP_IRQ_ACKFD_DEASSERT */
    +#define KVM_IRQ_ACKFD_FLAG_DEASSERT (1 << 2)

    struct kvm_irq_ackfd {
    __u32 flags;
    diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
    index ff5c784..ffc6a13 100644
    --- a/virt/kvm/eventfd.c
    +++ b/virt/kvm/eventfd.c
    @@ -682,6 +682,7 @@ kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)

    struct _irq_ackfd {
    struct kvm *kvm;
    + bool deassert; /* de-assert on ack? */
    struct eventfd_ctx *eventfd; /* signaled on ack */
    struct kvm_irq_ack_notifier notifier;
    /* Setup/shutdown */
    @@ -805,6 +806,10 @@ static void irq_ackfd_acked(struct kvm_irq_ack_notifier *notifier)

    ackfd = container_of(notifier, struct _irq_ackfd, notifier);

    + if (ackfd->deassert)
    + kvm_set_irq(ackfd->kvm, ackfd->notifier.irq_source_id,
    + ackfd->notifier.gsi, 0);
    +
    eventfd_signal(ackfd->eventfd, 1);
    }

    @@ -845,6 +850,12 @@ static int kvm_assign_irq_ackfd(struct kvm *kvm, struct kvm_irq_ackfd *args)
    ackfd->notifier.irq_source_id = -1;
    ackfd->notifier.irq_acked = irq_ackfd_acked;

    + ackfd->deassert = args->flags & KVM_IRQ_ACKFD_FLAG_DEASSERT;
    + if (ackfd->deassert && ackfd->notifier.irq_source_id < 0) {
    + ret = -EINVAL;
    + goto fail;
    + }
    +
    /*
    * Install our own custom wake-up handling so we are notified via
    * a callback whenever someone releases the underlying eventfd
    @@ -945,7 +956,8 @@ fail:
    int kvm_irq_ackfd(struct kvm *kvm, struct kvm_irq_ackfd *args)
    {
    if (args->flags & ~(KVM_IRQ_ACKFD_FLAG_DEASSIGN |
    - KVM_IRQ_ACKFD_FLAG_IRQ_SOURCE_ID))
    + KVM_IRQ_ACKFD_FLAG_IRQ_SOURCE_ID |
    + KVM_IRQ_ACKFD_FLAG_DEASSERT))
    return -EINVAL;

    if (args->flags & KVM_IRQ_ACKFD_FLAG_DEASSIGN)


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