linux-kernel - [PATCH RFC 3/3] Revert "virtio_ring: enable premapped mode whatever use_dma

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Message-ID: <4937ef0c9389fd2031cd0be78ae791d3289b6e94.1723617902.git.mst@redhat.com>
Date: Wed, 14 Aug 2024 02:59:31 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Jason Wang <jasowang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	virtualization@...ts.linux.dev,
	Darren Kenny <darren.kenny@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Si-Wei Liu <si-wei.liu@...cle.com>,
	Eugenio Pérez <eperezma@...hat.com>
Subject: [PATCH RFC 3/3] Revert "virtio_ring: enable premapped mode whatever
 use_dma_api"

This reverts commit f9dac92ba9081062a6477ee015bd3b8c5914efc4.

leads to crashes with no ACCESS_PLATFORM when
sysctl net.core.high_order_alloc_disable=1

Reported-by: Si-Wei Liu <si-wei.liu@...cle.com>
Message-ID: <8b20cc28-45a9-4643-8e87-ba164a540c0a@...cle.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/virtio/virtio_ring.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index be7309b1e860..06b5bdf0920e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2782,7 +2782,7 @@ EXPORT_SYMBOL_GPL(virtqueue_resize);
  *
  * Returns zero or a negative error.
  * 0: success.
- * -EINVAL: too late to enable premapped mode, the vq already contains buffers.
+ * -EINVAL: vring does not use the dma api, so we can not enable premapped mode.
  */
 int virtqueue_set_dma_premapped(struct virtqueue *_vq)
 {
@@ -2798,6 +2798,11 @@ int virtqueue_set_dma_premapped(struct virtqueue *_vq)
 		return -EINVAL;
 	}
 
+	if (!vq->use_dma_api) {
+		END_USE(vq);
+		return -EINVAL;
+	}
+
 	vq->premapped = true;
 	vq->do_unmap = false;
 
-- 
MST