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.
To unbreak legacy setups that may generate IRQ before DRIVER_OK, a
module parameter is introduced to disable the hardening by
default. The features can then be turned on the setups that the
hardening is needed (e.g the confidential computing and other cases).
Please review.
Thanks
Jason Wang (2):
virtio: use virtio_reset_device() when possible
virtio: harden vring IRQ
Stefano Garzarella (1):
virtio: use virtio_device_ready() in virtio_device_restore()
drivers/virtio/virtio.c | 28 ++++++++++++++++++++++++----
drivers/virtio/virtio_ring.c | 9 ++++++++-
include/linux/virtio.h | 4 ++++
include/linux/virtio_config.h | 25 +++++++++++++++++++++++++
4 files changed, 61 insertions(+), 5 deletions(-)
--
2.25.1
Jason Wang
2022-Mar-24 08:40 UTC
[PATCH 1/3] virtio: use virtio_device_ready() in virtio_device_restore()
From: Stefano Garzarella <sgarzare at redhat.com> This avoids setting DRIVER_OK twice for those drivers that call virtio_device_ready() in the .restore and it will allows us to do extension on virtio_device_ready() without duplicating codes. 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-Mar-24 08:40 UTC
[PATCH 2/3] virtio: use virtio_reset_device() when possible
This allows us to do common extension without duplicating codes. 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
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 irq_soft_enabled variable for each
virtio_device. Then we can to toggle it during
virtio_reset_device()/virtio_device_ready(). A synchornize_rcu() is
used in virtio_reset_device() to synchronize with the IRQ handlers. In
the future, we may provide config_ops for the transport that doesn't
use IRQ. With this, vring_interrupt() can return check and early if
irq_soft_enabled is false. This lead to smp_load_acquire() to be used
but the cost should be acceptable.
To avoid breaking legacy device which can send IRQ before DRIVER_OK, a
module parameter is introduced to enable the hardening so function
hardening is disabled by default.
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.
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
drivers/virtio/virtio.c | 19 +++++++++++++++++++
drivers/virtio/virtio_ring.c | 9 ++++++++-
include/linux/virtio.h | 4 ++++
include/linux/virtio_config.h | 25 +++++++++++++++++++++++++
4 files changed, 56 insertions(+), 1 deletion(-)
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index 8dde44ea044a..85e331efa9cc 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -7,6 +7,12 @@
#include <linux/of.h>
#include <uapi/linux/virtio_ids.h>
+static bool irq_hardening = false;
+
+module_param(irq_hardening, bool, 0444);
+MODULE_PARM_DESC(irq_hardening,
+ "Disalbe IRQ software processing when it is not expected");
+
/* Unique numbering for virtio devices. */
static DEFINE_IDA(virtio_index_ida);
@@ -220,6 +226,15 @@ static int virtio_features_ok(struct virtio_device *dev)
* */
void virtio_reset_device(struct virtio_device *dev)
{
+ /*
+ * The below synchronize_rcu() guarantees that any
+ * interrupt for this line arriving after
+ * synchronize_rcu() has completed is guaranteed to see
+ * irq_soft_enabled == false.
+ */
+ WRITE_ONCE(dev->irq_soft_enabled, false);
+ synchronize_rcu();
+
dev->config->reset(dev);
}
EXPORT_SYMBOL_GPL(virtio_reset_device);
@@ -427,6 +442,10 @@ int register_virtio_device(struct virtio_device *dev)
spin_lock_init(&dev->config_lock);
dev->config_enabled = false;
dev->config_change_pending = false;
+ dev->irq_soft_check = irq_hardening;
+
+ if (dev->irq_soft_check)
+ dev_info(&dev->dev, "IRQ hardening is enabled\n");
/* We always start by resetting the device, in case a previous
* driver messed it up. This also tests that code path a little. */
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 962f1477b1fa..0170f8c784d8 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2144,10 +2144,17 @@ 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 (!virtio_irq_soft_enabled(vdev)) {
+ 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..957d6ad604ac 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -95,6 +95,8 @@ 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
+ * @irq_soft_check: whether or not to check @irq_soft_enabled
+ * @irq_soft_enabled: callbacks enabled
* @config_lock: protects configuration change reporting
* @dev: underlying device.
* @id: the device type identification (used to match it with a driver).
@@ -109,6 +111,8 @@ struct virtio_device {
bool failed;
bool config_enabled;
bool config_change_pending;
+ bool irq_soft_check;
+ bool irq_soft_enabled;
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 dafdc7f48c01..9c1b61f2e525 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -174,6 +174,24 @@ static inline bool virtio_has_feature(const struct
virtio_device *vdev,
return __virtio_test_bit(vdev, fbit);
}
+/*
+ * virtio_irq_soft_enabled: whether we can execute callbacks
+ * @vdev: the device
+ */
+static inline bool virtio_irq_soft_enabled(const struct virtio_device *vdev)
+{
+ if (!vdev->irq_soft_check)
+ return true;
+
+ /*
+ * Read irq_soft_enabled before reading other device specific
+ * data. Paried with smp_store_relase() in
+ * virtio_device_ready() and WRITE_ONCE()/synchronize_rcu() in
+ * virtio_reset_device().
+ */
+ return smp_load_acquire(&vdev->irq_soft_enabled);
+}
+
/**
* virtio_has_dma_quirk - determine whether this device has the DMA quirk
* @vdev: the device
@@ -236,6 +254,13 @@ void virtio_device_ready(struct virtio_device *dev)
if (dev->config->enable_cbs)
dev->config->enable_cbs(dev);
+ /*
+ * Commit the driver setup before enabling the virtqueue
+ * callbacks. Paried with smp_load_acuqire() in
+ * virtio_irq_soft_enabled()
+ */
+ smp_store_release(&dev->irq_soft_enabled, true);
+
BUG_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
}
--
2.25.1