linux-kernel - [PATCH 4.9 15/28] virtio_mmio: Restore guest page size on resume

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Message-Id: <20220719114457.698901288@linuxfoundation.org>
Date:   Tue, 19 Jul 2022 13:53:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Stephan Gerhold <stephan.gerhold@...nkonzept.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 15/28] virtio_mmio: Restore guest page size on resume

From: Stephan Gerhold <stephan.gerhold@...nkonzept.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@...nkonzept.com>
Message-Id: <20220621110621.3638025-3-stephan.gerhold@...nkonzept.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.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 d69f0c5135ff..413f6af4d132 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -502,6 +502,9 @@ 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