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Date: Mon, 1 Aug 2022 09:39:41 +0000
From: Alexander Atanasov <alexander.atanasov@...tuozzo.com>
To: "Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>
Cc: kernel@...nvz.org,
Alexander Atanasov <alexander.atanasov@...tuozzo.com>,
virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/1] virtio: Restore semantics of vq->broken in virtqueues and improve irq handling
virtio: harden vring IRQ (8b4ec69d7e09) changed the meaning
of vq->broken which results in vring_interrupt handles IRQs for
broken drivers as IRQ_NONE and not IRQ_HANDLED and made impossible
to initiallize vqs before the driver is ready, i.e. in probe method.
Balloon driver does this and it can not load because it fails in
vqs_init with -EIO.
So instead of changing the original intent ot the flag introduce
a new flag vq->ready which servers the purpose to check of early IRQs.
With the new flag improve the logic of IRQ handling like this:
Until the driver is ready return IRQ_HANDLED so the IRQ does not get
disabled while starting up.
If the driver gets broken return IRQ_NONE so the IRQ gets disabled.
Signed-off-by: Alexander Atanasov <alexander.atanasov@...tuozzo.com>
---
drivers/virtio/virtio_ring.c | 34 ++++++++++++++++++++++------------
include/linux/virtio.h | 4 +++-
include/linux/virtio_config.h | 12 ++++++------
3 files changed, 31 insertions(+), 19 deletions(-)
V2:
Reworked on top of config option to disable the hardening.
V3:
Changed irq handling logic depending on the flags
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 643ca779fcc6..a385d563c71f 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -100,6 +100,9 @@ struct vring_virtqueue {
/* Other side has made a mess, don't try any more. */
bool broken;
+ /* the queue is ready to handle interrupts */
+ bool ready;
+
/* Host supports indirect buffers */
bool indirect;
@@ -1708,10 +1711,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
vq->we_own_ring = true;
vq->notify = notify;
vq->weak_barriers = weak_barriers;
-#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
- vq->broken = true;
-#else
vq->broken = false;
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+ vq->ready = false;
#endif
vq->last_used_idx = 0 | (1 << VRING_PACKED_EVENT_F_WRAP_CTR);
vq->event_triggered = false;
@@ -2160,13 +2162,21 @@ irqreturn_t vring_interrupt(int irq, void *_vq)
if (unlikely(vq->broken)) {
#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
dev_warn_once(&vq->vq.vdev->dev,
- "virtio vring IRQ raised before DRIVER_OK");
+ "virtio vring IRQ raised for broken vq");
return IRQ_NONE;
#else
return IRQ_HANDLED;
#endif
}
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+ if (unlikely(!vq->ready)) {
+ dev_warn_once(&vq->vq.vdev->dev,
+ "virtio vring IRQ raised before DRIVER_OK");
+ return IRQ_HANDLED;
+ }
+#endif
+
/* Just a hint for performance: so it's ok that this can be racy! */
if (vq->event)
vq->event_triggered = true;
@@ -2207,10 +2217,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
vq->we_own_ring = false;
vq->notify = notify;
vq->weak_barriers = weak_barriers;
-#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
- vq->broken = true;
-#else
vq->broken = false;
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+ vq->ready = false;
#endif
vq->last_used_idx = 0;
vq->event_triggered = false;
@@ -2429,14 +2438,15 @@ void virtio_break_device(struct virtio_device *dev)
}
EXPORT_SYMBOL_GPL(virtio_break_device);
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
/*
* This should allow the device to be used by the driver. You may
* need to grab appropriate locks to flush the write to
- * vq->broken. This should only be used in some specific case e.g
+ * vq->ready. This should only be used in some specific case e.g
* (probing and restoring). This function should only be called by the
* core, not directly by the driver.
*/
-void __virtio_unbreak_device(struct virtio_device *dev)
+void __virtio_device_ready(struct virtio_device *dev)
{
struct virtqueue *_vq;
@@ -2444,12 +2454,12 @@ void __virtio_unbreak_device(struct virtio_device *dev)
list_for_each_entry(_vq, &dev->vqs, list) {
struct vring_virtqueue *vq = to_vvq(_vq);
- /* Pairs with READ_ONCE() in virtqueue_is_broken(). */
- WRITE_ONCE(vq->broken, false);
+ WRITE_ONCE(vq->ready, true);
}
spin_unlock(&dev->vqs_list_lock);
}
-EXPORT_SYMBOL_GPL(__virtio_unbreak_device);
+EXPORT_SYMBOL_GPL(__virtio_device_ready);
+#endif
dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
{
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d8fdf170637c..a63120477ae1 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -131,7 +131,9 @@ void unregister_virtio_device(struct virtio_device *dev);
bool is_virtio_device(struct device *dev);
void virtio_break_device(struct virtio_device *dev);
-void __virtio_unbreak_device(struct virtio_device *dev);
+#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
+void __virtio_device_ready(struct virtio_device *dev);
+#endif
void virtio_config_changed(struct virtio_device *dev);
#ifdef CONFIG_PM_SLEEP
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index b47c2e7ed0ee..472d4703d499 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -260,22 +260,22 @@ void virtio_device_ready(struct virtio_device *dev)
#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
/*
* The virtio_synchronize_cbs() makes sure vring_interrupt()
- * will see the driver specific setup if it sees vq->broken
- * as false (even if the notifications come before DRIVER_OK).
+ * will see the driver specific setup if it sees vq->ready
+ * as true (even if the notifications come before DRIVER_OK).
*/
virtio_synchronize_cbs(dev);
- __virtio_unbreak_device(dev);
+ __virtio_device_ready(dev);
#endif
/*
- * The transport should ensure the visibility of vq->broken
+ * The transport should ensure the visibility of vq->ready
* before setting DRIVER_OK. See the comments for the transport
* specific set_status() method.
*
* A well behaved device will only notify a virtqueue after
* DRIVER_OK, this means the device should "see" the coherenct
- * memory write that set vq->broken as false which is done by
+ * memory write that set vq->ready as true which is done by
* the driver when it sees DRIVER_OK, then the following
- * driver's vring_interrupt() will see vq->broken as false so
+ * driver's vring_interrupt() will see vq->ready as true so
* we won't lose any notification.
*/
dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
--
2.25.1
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