thr3ads.net - Virtualization - [PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks [Apr 2022]

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Jason Wang

2022-Apr-06 08:35 UTC

[PATCH V2 0/5] rework on the IRQ hardening of virtio

Hi All:

This is a rework on the IRQ hardening for virtio which is done
previously by the following commits are reverted:

9e35276a5344 ("virtio_pci: harden MSI-X interrupts")
080cd7c3ac87 ("virtio-pci: harden INTX interrupts")

The reason is that it depends on the IRQF_NO_AUTOEN which may conflict
with the assumption of the affinity managed IRQ that is used by some
virtio drivers. And what's more, it is only done for virtio-pci but
not other transports.

In this rework, I try to implement a general virtio solution which
borrows the idea of the INTX hardening by introducing a boolean for
virtqueue callback enabling and toggle it in virtio_device_ready()
and virtio_reset_device(). Then vring_interrupt() can simply check and
return early if the driver is not ready.

Please review.

Changes since v1:

- Use transport specific irq synchronization method when possible
- Drop the module parameter and enable the hardening unconditonally
- Tweak the barrier/ordering facilities used in the code
- Reanme irq_soft_enabled to driver_ready
- Avoid unnecssary IRQ synchornization (e.g during boot)

Jason Wang (4):
  virtio: use virtio_reset_device() when possible
  virtio: introduce config op to synchronize vring callbacks
  virtio-pci: implement synchronize_vqs()
  virtio: harden vring IRQ

Stefano Garzarella (1):
  virtio: use virtio_device_ready() in virtio_device_restore()

 drivers/virtio/virtio.c            | 20 ++++++++++++++++----
 drivers/virtio/virtio_pci_common.c | 14 ++++++++++++++
 drivers/virtio/virtio_pci_common.h |  2 ++
 drivers/virtio/virtio_pci_legacy.c |  1 +
 drivers/virtio/virtio_pci_modern.c |  2 ++
 drivers/virtio/virtio_ring.c       |  9 ++++++++-
 include/linux/virtio.h             |  2 ++
 include/linux/virtio_config.h      | 24 ++++++++++++++++++++++++
 8 files changed, 69 insertions(+), 5 deletions(-)

-- 
2.25.1

Jason Wang

2022-Apr-06 08:35 UTC

head link

[PATCH V2 1/5] virtio: use virtio_device_ready() in virtio_device_restore()

From: Stefano Garzarella <sgarzare at redhat.com>

It will allows us to do extension on virtio_device_ready() without
duplicating codes.

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/virtio.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 22f15f444f75..75c8d560bbd3 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -526,8 +526,9 @@ int virtio_device_restore(struct virtio_device *dev)
 			goto err;
 	}
 
-	/* Finally, tell the device we're all set */
-	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
+	/* If restore didn't do it, mark device DRIVER_OK ourselves. */
+	if (!(dev->config->get_status(dev) & VIRTIO_CONFIG_S_DRIVER_OK))
+		virtio_device_ready(dev);
 
 	virtio_config_enable(dev);
 
-- 
2.25.1

Jason Wang

2022-Apr-06 08:35 UTC

head link

[PATCH V2 2/5] virtio: use virtio_reset_device() when possible

This allows us to do common extension without duplicating codes.

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/virtio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 75c8d560bbd3..8dde44ea044a 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -430,7 +430,7 @@ int register_virtio_device(struct virtio_device *dev)
 
 	/* We always start by resetting the device, in case a previous
 	 * driver messed it up.  This also tests that code path a little. */
-	dev->config->reset(dev);
+	virtio_reset_device(dev);
 
 	/* Acknowledge that we've seen the device. */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
@@ -496,7 +496,7 @@ int virtio_device_restore(struct virtio_device *dev)
 
 	/* We always start by resetting the device, in case a previous
 	 * driver messed it up. */
-	dev->config->reset(dev);
+	virtio_reset_device(dev);
 
 	/* Acknowledge that we've seen the device. */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
-- 
2.25.1

Jason Wang

2022-Apr-06 08:35 UTC

head link

[PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks

This patch introduce a new virtio config ops to vring
callbacks. Transport specific method is required to call
synchornize_irq() on the IRQs. For the transport that doesn't provide
synchronize_vqs(), use synchornize_rcu() as a fallback.

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 include/linux/virtio_config.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index b341dd62aa4d..08b73d9bbff2 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -57,6 +57,8 @@ struct virtio_shm_region {
  *		include a NULL entry for vqs unused by driver
  *	Returns 0 on success or error status
  * @del_vqs: free virtqueues found by find_vqs().
+ * @synchronize_vqs: synchronize with the virtqueue callbacks.
+ *	vdev: the virtio_device
  * @get_features: get the array of feature bits for this device.
  *	vdev: the virtio_device
  *	Returns the first 64 feature bits (all we currently need).
@@ -89,6 +91,7 @@ struct virtio_config_ops {
 			const char * const names[], const bool *ctx,
 			struct irq_affinity *desc);
 	void (*del_vqs)(struct virtio_device *);
+	void (*synchronize_vqs)(struct virtio_device *);
 	u64 (*get_features)(struct virtio_device *vdev);
 	int (*finalize_features)(struct virtio_device *vdev);
 	const char *(*bus_name)(struct virtio_device *vdev);
@@ -217,6 +220,19 @@ int virtio_find_vqs_ctx(struct virtio_device *vdev,
unsigned nvqs,
 				      desc);
 }
 
+/**
+ * virtio_synchronize_vqs - synchronize with virtqueue callbacks
+ * @vdev: the device
+ */
+static inline
+void virtio_synchronize_vqs(struct virtio_device *dev)
+{
+	if (dev->config->synchronize_vqs)
+		dev->config->synchronize_vqs(dev);
+	else
+		synchronize_rcu();
+}
+
 /**
  * virtio_device_ready - enable vq use in probe function
  * @vdev: the device
-- 
2.25.1

Jason Wang

2022-Apr-06 08:35 UTC

head link

[PATCH V2 4/5] virtio-pci: implement synchronize_vqs()

This patch implements PCI version of synchronize_vqs().

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/virtio_pci_common.c | 14 ++++++++++++++
 drivers/virtio/virtio_pci_common.h |  2 ++
 drivers/virtio/virtio_pci_legacy.c |  1 +
 drivers/virtio/virtio_pci_modern.c |  2 ++
 4 files changed, 19 insertions(+)

diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index d724f676608b..b78c8bc93a97 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -37,6 +37,20 @@ void vp_synchronize_vectors(struct virtio_device *vdev)
 		synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
 }
 
+void vp_synchronize_vqs(struct virtio_device *vdev)
+{
+	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+	int i;
+
+	if (vp_dev->intx_enabled) {
+		synchronize_irq(vp_dev->pci_dev->irq);
+		return;
+	}
+
+	for (i = 0; i < vp_dev->msix_vectors; ++i)
+		synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
+}
+
 /* the notify function used when creating a virt queue */
 bool vp_notify(struct virtqueue *vq)
 {
diff --git a/drivers/virtio/virtio_pci_common.h
b/drivers/virtio/virtio_pci_common.h
index eb17a29fc7ef..2b84d5c1b5bc 100644
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -105,6 +105,8 @@ static struct virtio_pci_device *to_vp_device(struct
virtio_device *vdev)
 void vp_synchronize_vectors(struct virtio_device *vdev);
 /* the notify function used when creating a virt queue */
 bool vp_notify(struct virtqueue *vq);
+/* synchronize with callbacks */
+void vp_synchronize_vqs(struct virtio_device *vdev);
 /* the config->del_vqs() implementation */
 void vp_del_vqs(struct virtio_device *vdev);
 /* the config->find_vqs() implementation */
diff --git a/drivers/virtio/virtio_pci_legacy.c
b/drivers/virtio/virtio_pci_legacy.c
index 6f4e34ce96b8..5a9e62320edc 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -192,6 +192,7 @@ static const struct virtio_config_ops virtio_pci_config_ops
= {
 	.reset		= vp_reset,
 	.find_vqs	= vp_find_vqs,
 	.del_vqs	= vp_del_vqs,
+	.synchronize_vqs = vp_synchronize_vqs,
 	.get_features	= vp_get_features,
 	.finalize_features = vp_finalize_features,
 	.bus_name	= vp_bus_name,
diff --git a/drivers/virtio/virtio_pci_modern.c
b/drivers/virtio/virtio_pci_modern.c
index a2671a20ef77..584850389855 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -394,6 +394,7 @@ static const struct virtio_config_ops
virtio_pci_config_nodev_ops = {
 	.reset		= vp_reset,
 	.find_vqs	= vp_modern_find_vqs,
 	.del_vqs	= vp_del_vqs,
+	.synchronize_vqs = vp_synchronize_vqs,
 	.get_features	= vp_get_features,
 	.finalize_features = vp_finalize_features,
 	.bus_name	= vp_bus_name,
@@ -411,6 +412,7 @@ static const struct virtio_config_ops virtio_pci_config_ops
= {
 	.reset		= vp_reset,
 	.find_vqs	= vp_modern_find_vqs,
 	.del_vqs	= vp_del_vqs,
+	.synchronize_vqs = vp_synchronize_vqs,
 	.get_features	= vp_get_features,
 	.finalize_features = vp_finalize_features,
 	.bus_name	= vp_bus_name,
-- 
2.25.1

Jason Wang

2022-Apr-06 08:35 UTC

head link

[PATCH V2 5/5] virtio: harden vring IRQ

This is a rework on the previous IRQ hardening that is done for
virtio-pci where several drawbacks were found and were reverted:

1) try to use IRQF_NO_AUTOEN which is not friendly to affinity managed IRQ
   that is used by some device such as virtio-blk
2) done only for PCI transport

In this patch, we tries to borrow the idea from the INTX IRQ hardening
in the reverted commit 080cd7c3ac87 ("virtio-pci: harden INTX
interrupts")
by introducing a global device_ready variable for each
virtio_device. Then we can to toggle it during
virtio_reset_device()/virtio_device_ready(). A
virtio_synchornize_vqs() is used in both virtio_device_ready() and
virtio_reset_device() to synchronize with the vring callbacks. With
this, vring_interrupt() can return check and early if driver_ready is
false.

Note that the hardening is only done for vring interrupt since the
config interrupt hardening is already done in commit 22b7050a024d7
("virtio: defer config changed notifications"). But the method that is
used by config interrupt can't be reused by the vring interrupt
handler because it uses spinlock to do the synchronization which is
expensive.

Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Marc Zyngier <maz at kernel.org>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
 drivers/virtio/virtio.c       | 11 +++++++++++
 drivers/virtio/virtio_ring.c  |  9 ++++++++-
 include/linux/virtio.h        |  2 ++
 include/linux/virtio_config.h |  8 ++++++++
 4 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 8dde44ea044a..2f3a6f8e3d9c 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -220,6 +220,17 @@ static int virtio_features_ok(struct virtio_device *dev)
  * */
 void virtio_reset_device(struct virtio_device *dev)
 {
+	if (READ_ONCE(dev->driver_ready)) {
+		/*
+		 * The below virtio_synchronize_vqs() guarantees that any
+		 * interrupt for this line arriving after
+		 * virtio_synchronize_vqs() has completed is guaranteed to see
+		 * driver_ready == false.
+		 */
+		WRITE_ONCE(dev->driver_ready, false);
+		virtio_synchronize_vqs(dev);
+	}
+
 	dev->config->reset(dev);
 }
 EXPORT_SYMBOL_GPL(virtio_reset_device);
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cfb028ca238e..a4592e55c9f8 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2127,10 +2127,17 @@ static inline bool more_used(const struct
vring_virtqueue *vq)
 	return vq->packed_ring ? more_used_packed(vq) : more_used_split(vq);
 }
 
-irqreturn_t vring_interrupt(int irq, void *_vq)
+irqreturn_t vring_interrupt(int irq, void *v)
 {
+	struct virtqueue *_vq = v;
+	struct virtio_device *vdev = _vq->vdev;
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
+	if (!READ_ONCE(vdev->driver_ready)) {
+		dev_warn_once(&vdev->dev, "virtio vring IRQ raised before
DRIVER_OK");
+		return IRQ_NONE;
+	}
+
 	if (!more_used(vq)) {
 		pr_debug("virtqueue interrupt with no work for %p\n", vq);
 		return IRQ_NONE;
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 5464f398912a..dfa2638a293e 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -95,6 +95,7 @@ dma_addr_t virtqueue_get_used_addr(struct virtqueue *vq);
  * @failed: saved value for VIRTIO_CONFIG_S_FAILED bit (for restore)
  * @config_enabled: configuration change reporting enabled
  * @config_change_pending: configuration change reported while disabled
+ * @driver_ready: whehter the driver is ready (e.g for vring callbacks)
  * @config_lock: protects configuration change reporting
  * @dev: underlying device.
  * @id: the device type identification (used to match it with a driver).
@@ -109,6 +110,7 @@ struct virtio_device {
 	bool failed;
 	bool config_enabled;
 	bool config_change_pending;
+	bool driver_ready;
 	spinlock_t config_lock;
 	spinlock_t vqs_list_lock; /* Protects VQs list access */
 	struct device dev;
diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 08b73d9bbff2..c9e207bf2c9c 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -246,6 +246,14 @@ void virtio_device_ready(struct virtio_device *dev)
 {
 	unsigned status = dev->config->get_status(dev);
 
+	virtio_synchronize_vqs(dev);
+        /*
+         * The above virtio_synchronize_vqs() make sure
+         * vring_interrupt() will see the driver specific setup if it
+         * see driver_ready as true.
+         */
+	WRITE_ONCE(dev->driver_ready, true);
+
 	BUG_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
 	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
 }
-- 
2.25.1

Michael S. Tsirkin

2022-Apr-06 11:36 UTC

head link

[PATCH V2 0/5] rework on the IRQ hardening of virtio

On Wed, Apr 06, 2022 at 04:35:33PM +0800, Jason Wang
wrote:> Hi All:
> 
> This is a rework on the IRQ hardening for virtio which is done
> previously by the following commits are reverted:
> 
> 9e35276a5344 ("virtio_pci: harden MSI-X interrupts")
> 080cd7c3ac87 ("virtio-pci: harden INTX interrupts")
> 
> The reason is that it depends on the IRQF_NO_AUTOEN which may conflict
> with the assumption of the affinity managed IRQ that is used by some
> virtio drivers. And what's more, it is only done for virtio-pci but
> not other transports.
> 
> In this rework, I try to implement a general virtio solution which
> borrows the idea of the INTX hardening by introducing a boolean for
> virtqueue callback enabling and toggle it in virtio_device_ready()
> and virtio_reset_device(). Then vring_interrupt() can simply check and
> return early if the driver is not ready.

All of a sudden all patches are having a wrong mime type.

It is application/octet-stream; should be text/plain

Pls fix and repost, thanks!
> Please review.
> 
> Changes since v1:
> 
> - Use transport specific irq synchronization method when possible
> - Drop the module parameter and enable the hardening unconditonally
> - Tweak the barrier/ordering facilities used in the code
> - Reanme irq_soft_enabled to driver_ready
> - Avoid unnecssary IRQ synchornization (e.g during boot)
> 
> Jason Wang (4):
>   virtio: use virtio_reset_device() when possible
>   virtio: introduce config op to synchronize vring callbacks
>   virtio-pci: implement synchronize_vqs()
>   virtio: harden vring IRQ
> 
> Stefano Garzarella (1):
>   virtio: use virtio_device_ready() in virtio_device_restore()
> 
>  drivers/virtio/virtio.c            | 20 ++++++++++++++++----
>  drivers/virtio/virtio_pci_common.c | 14 ++++++++++++++
>  drivers/virtio/virtio_pci_common.h |  2 ++
>  drivers/virtio/virtio_pci_legacy.c |  1 +
>  drivers/virtio/virtio_pci_modern.c |  2 ++
>  drivers/virtio/virtio_ring.c       |  9 ++++++++-
>  include/linux/virtio.h             |  2 ++
>  include/linux/virtio_config.h      | 24 ++++++++++++++++++++++++
>  8 files changed, 69 insertions(+), 5 deletions(-)
> 
> -- 
> 2.25.1

Virtualization - Apr 2022 - [PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks

[PATCH V2 0/5] rework on the IRQ hardening of virtio

[PATCH V2 1/5] virtio: use virtio_device_ready() in virtio_device_restore()

[PATCH V2 2/5] virtio: use virtio_reset_device() when possible

[PATCH V2 3/5] virtio: introduce config op to synchronize vring callbacks

[PATCH V2 4/5] virtio-pci: implement synchronize_vqs()

[PATCH V2 5/5] virtio: harden vring IRQ

[PATCH V2 0/5] rework on the IRQ hardening of virtio