[PATCH 5.10 078/112] virtio_mmio: Restore guest page size on resume

Greg Kroah-Hartman
2022-07-19T12:25:05Z

From: Stephan Gerhold <stephan.gerhold@kernkonzept.com>

[ Upstream commit e0c2ce8217955537dd5434baeba061f209797119 ]

Virtio devices might lose their state when the VMM is restarted
after a suspend to disk (hibernation) cycle. This means that the
guest page size register must be restored for the virtio_mmio legacy
interface, since otherwise the virtio queues are not functional.

This is particularly problematic for QEMU that currently still defaults
to using the legacy interface for virtio_mmio. Write the guest page
size register again in virtio_mmio_restore() to make legacy virtio_mmio
devices work correctly after hibernation.

Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Message-Id: <20220621110621.3638025-3-stephan.gerhold@kernkonzept.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/virtio/virtio_mmio.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 7dec1418bf7c..e8ef0c66e558 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -556,6 +556,9 @@ static int virtio_mmio_restore(struct device *dev)
{
struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);

+ if (vm_dev->version == 1)
+ writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
+
return virtio_device_restore(&vm_dev->vdev);
}

--
2.35.1