[PATCH AUTOSEL 5.4 02/10] virtio: Improve vq->broken access to avoid any compiler optimization

[PATCH AUTOSEL 5.4 02/10] virtio: Improve vq->broken access to avoid any compiler optimization

[Sasha Levin]

From: Parav Pandit <parav@nvidia.com>

[ Upstream commit 60f0779862e4ab943810187752c462e85f5fa371 ]

Currently vq->broken field is read by virtqueue_is_broken() in busy
loop in one context by virtnet_send_command().

vq->broken is set to true in other process context by
virtio_break_device(). Reader and writer are accessing it without any
synchronization. This may lead to a compiler optimization which may
result to optimize reading vq->broken only once.

Hence, force reading vq->broken on each invocation of
virtqueue_is_broken() and also force writing it so that such
update is visible to the readers.

It is a theoretical fix that isn't yet encountered in the field.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Link: https://lore.kernel.org/r/20210721142648.1525924-2-parav@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/virtio/virtio_ring.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 97e8a195e18f..c9550b7291e7 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2262,7 +2262,7 @@ bool virtqueue_is_broken(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
-	return vq->broken;
+	return READ_ONCE(vq->broken);
 }
 EXPORT_SYMBOL_GPL(virtqueue_is_broken);
 
@@ -2276,7 +2276,9 @@ void virtio_break_device(struct virtio_device *dev)
 
 	list_for_each_entry(_vq, &dev->vqs, list) {
 		struct vring_virtqueue *vq = to_vvq(_vq);
-		vq->broken = true;
+
+		/* Pairs with READ_ONCE() in virtqueue_is_broken(). */
+		WRITE_ONCE(vq->broken, true);
 	}
 }
 EXPORT_SYMBOL_GPL(virtio_break_device);
-- 
2.30.2

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[PATCH AUTOSEL 5.4 03/10] virtio_pci: Support surprise removal of virtio pci device

[Sasha Levin]

From: Parav Pandit <parav@nvidia.com>

[ Upstream commit 43bb40c5b92659966bdf4bfe584fde0a3575a049 ]

When a virtio pci device undergo surprise removal (aka async removal in
PCIe spec), mark the device as broken so that any upper layer drivers can
abort any outstanding operation.

When a virtio net pci device undergo surprise removal which is used by a
NetworkManager, a below call trace was observed.

kernel:watchdog: BUG: soft lockup - CPU#1 stuck for 26s! [kworker/1:1:27059]
watchdog: BUG: soft lockup - CPU#1 stuck for 52s! [kworker/1:1:27059]
CPU: 1 PID: 27059 Comm: kworker/1:1 Tainted: G S      W I  L    5.13.0-hotplug+ #8
Hardware name: Dell Inc. PowerEdge R640/0H28RR, BIOS 2.9.4 11/06/2020
Workqueue: events linkwatch_event
RIP: 0010:virtnet_send_command+0xfc/0x150 [virtio_net]
Call Trace:
 virtnet_set_rx_mode+0xcf/0x2a7 [virtio_net]
 ? __hw_addr_create_ex+0x85/0xc0
 __dev_mc_add+0x72/0x80
 igmp6_group_added+0xa7/0xd0
 ipv6_mc_up+0x3c/0x60
 ipv6_find_idev+0x36/0x80
 addrconf_add_dev+0x1e/0xa0
 addrconf_dev_config+0x71/0x130
 addrconf_notify+0x1f5/0xb40
 ? rtnl_is_locked+0x11/0x20
 ? __switch_to_asm+0x42/0x70
 ? finish_task_switch+0xaf/0x2c0
 ? raw_notifier_call_chain+0x3e/0x50
 raw_notifier_call_chain+0x3e/0x50
 netdev_state_change+0x67/0x90
 linkwatch_do_dev+0x3c/0x50
 __linkwatch_run_queue+0xd2/0x220
 linkwatch_event+0x21/0x30
 process_one_work+0x1c8/0x370
 worker_thread+0x30/0x380
 ? process_one_work+0x370/0x370
 kthread+0x118/0x140
 ? set_kthread_struct+0x40/0x40
 ret_from_fork+0x1f/0x30

Hence, add the ability to abort the command on surprise removal
which prevents infinite loop and system lockup.

Signed-off-by: Parav Pandit <parav@nvidia.com>
Link: https://lore.kernel.org/r/20210721142648.1525924-5-parav@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/virtio/virtio_pci_common.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 222d630c41fc..b35bb2d57f62 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -576,6 +576,13 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
 	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
 	struct device *dev = get_device(&vp_dev->vdev.dev);
 
+	/*
+	 * Device is marked broken on surprise removal so that virtio upper
+	 * layers can abort any ongoing operation.
+	 */
+	if (!pci_device_is_present(pci_dev))
+		virtio_break_device(&vp_dev->vdev);
+
 	pci_disable_sriov(pci_dev);
 
 	unregister_virtio_device(&vp_dev->vdev);
-- 
2.30.2

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[PATCH AUTOSEL 5.4 04/10] vringh: Use wiov->used to check for read/write desc order

[Sasha Levin]

From: Neeraj Upadhyay <neeraju@codeaurora.org>

[ Upstream commit e74cfa91f42c50f7f649b0eca46aa049754ccdbd ]

As __vringh_iov() traverses a descriptor chain, it populates
each descriptor entry into either read or write vring iov
and increments that iov's ->used member. So, as we iterate
over a descriptor chain, at any point, (riov/wriov)->used
value gives the number of descriptor enteries available,
which are to be read or written by the device. As all read
iovs must precede the write iovs, wiov->used should be zero
when we are traversing a read descriptor. Current code checks
for wiov->i, to figure out whether any previous entry in the
current descriptor chain was a write descriptor. However,
iov->i is only incremented, when these vring iovs are consumed,
at a later point, and remain 0 in __vringh_iov(). So, correct
the check for read and write descriptor order, to use
wiov->used.

Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Link: https://lore.kernel.org/r/1624591502-4827-1-git-send-email-neeraju@codeaurora.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/vhost/vringh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 026a37ee4177..4653de001e26 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -331,7 +331,7 @@ __vringh_iov(struct vringh *vrh, u16 i,
 			iov = wiov;
 		else {
 			iov = riov;
-			if (unlikely(wiov && wiov->i)) {
+			if (unlikely(wiov && wiov->used)) {
 				vringh_bad("Readable desc %p after writable",
 					   &descs[i]);
 				err = -EINVAL;
-- 
2.30.2

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