From: Longjun Tang <[email protected]> In the vring_interrupt, if the used ring is empty, IRQ_NONE is returned. However,Sometimes, such as with busy-polling, buffers might be consumed from the used ring before an stale interrupt notification arrives. it leading to return IRQ_NONE.
The kernel's spurious-IRQ detector counts consecutive IRQ_NONE returns and will permanently disable the interrupt line if 99,900 out of 100,000 interrupts go unhandled. Add is_cb_disabled() to virtqueue_ops and, when more_used() is false but cb are suppressed, return IRQ_HANDLED instead of IRQ_NONE so the spurious counter does not accumulate. Signed-off-by: Longjun Tang <[email protected]> --- drivers/virtio/virtio_ring.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 335692d41617..52df932fc4a2 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -185,6 +185,7 @@ struct virtqueue_ops { unsigned int last_used_idx); void *(*detach_unused_buf)(struct vring_virtqueue *vq); bool (*more_used)(const struct vring_virtqueue *vq); + bool (*is_cb_disabled)(const struct vring_virtqueue *vq); int (*resize)(struct vring_virtqueue *vq, u32 num); void (*reset)(struct vring_virtqueue *vq); }; @@ -1063,6 +1064,12 @@ static void virtqueue_disable_cb_split(struct vring_virtqueue *vq) } } +static bool is_cb_disabled_split(const struct vring_virtqueue *vq) +{ + return !!(data_race(vq->split.avail_flags_shadow) & + VRING_AVAIL_F_NO_INTERRUPT); +} + static unsigned int virtqueue_enable_cb_prepare_split(struct vring_virtqueue *vq) { u16 last_used_idx; @@ -2227,6 +2234,12 @@ static void virtqueue_disable_cb_packed(struct vring_virtqueue *vq) } } +static bool is_cb_disabled_packed(const struct vring_virtqueue *vq) +{ + return data_race(vq->packed.event_flags_shadow) == + VRING_PACKED_EVENT_FLAG_DISABLE; +} + static unsigned int virtqueue_enable_cb_prepare_packed(struct vring_virtqueue *vq) { START_USE(vq); @@ -2644,6 +2657,7 @@ static const struct virtqueue_ops split_ops = { .poll = virtqueue_poll_split, .detach_unused_buf = virtqueue_detach_unused_buf_split, .more_used = more_used_split, + .is_cb_disabled = is_cb_disabled_split, .resize = virtqueue_resize_split, .reset = virtqueue_reset_split, }; @@ -2658,6 +2672,7 @@ static const struct virtqueue_ops packed_ops = { .poll = virtqueue_poll_packed, .detach_unused_buf = virtqueue_detach_unused_buf_packed, .more_used = more_used_packed, + .is_cb_disabled = is_cb_disabled_packed, .resize = virtqueue_resize_packed, .reset = virtqueue_reset_packed, }; @@ -2672,6 +2687,7 @@ static const struct virtqueue_ops split_in_order_ops = { .poll = virtqueue_poll_split, .detach_unused_buf = virtqueue_detach_unused_buf_split, .more_used = more_used_split_in_order, + .is_cb_disabled = is_cb_disabled_split, .resize = virtqueue_resize_split, .reset = virtqueue_reset_split, }; @@ -2686,6 +2702,7 @@ static const struct virtqueue_ops packed_in_order_ops = { .poll = virtqueue_poll_packed, .detach_unused_buf = virtqueue_detach_unused_buf_packed, .more_used = more_used_packed_in_order, + .is_cb_disabled = is_cb_disabled_packed, .resize = virtqueue_resize_packed, .reset = virtqueue_reset_packed, }; @@ -3231,6 +3248,18 @@ irqreturn_t vring_interrupt(int irq, void *_vq) struct vring_virtqueue *vq = to_vvq(_vq); if (!more_used(vq)) { + /* + * Stale interrupt: the device posted this notification + * before it observed the callback suppression; + * When more_used returns empty, IRQ_HANDLED should be + * returned for stale interrupts. + */ + if (VIRTQUEUE_CALL(vq, is_cb_disabled)) { + if (vq->event) + data_race(vq->event_triggered = true); + pr_debug("virtqueue stale interrupt (callbacks disabled) for %p\n", vq); + return IRQ_HANDLED; + } pr_debug("virtqueue interrupt with no work for %p\n", vq); return IRQ_NONE; } -- 2.43.0
