linux-kernel - [PATCH RFC 12/13] virtio_input: use virtqueue_add_inbuf_cache

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Message-ID: <797e9046d85137053c86012de026cd1aefcd02ad.1767089672.git.mst@redhat.com>
Date: Tue, 30 Dec 2025 05:16:25 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Cong Wang <xiyou.wangcong@...il.com>, Jonathan Corbet <corbet@....net>,
	Olivia Mackall <olivia@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Jason Wang <jasowang@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	"James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
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	linux-doc@...r.kernel.org, linux-crypto@...r.kernel.org,
	virtualization@...ts.linux.dev, linux-scsi@...r.kernel.org,
	iommu@...ts.linux.dev, kvm@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH RFC 12/13] virtio_input: use virtqueue_add_inbuf_cache_clean
 for events

The evts array contains 64 small (8-byte) input events that share
cachelines with each other. When CONFIG_DMA_API_DEBUG is enabled,
this can trigger warnings about overlapping DMA mappings within
the same cacheline.

Previous patch isolated the array in its own cachelines,
so the warnings are now spurious.

Use virtqueue_add_inbuf_cache_clean() to indicate that the CPU does not
write into these cache lines, suppressing these warnings.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/virtio/virtio_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_input.c b/drivers/virtio/virtio_input.c
index 774494754a99..b26db7d6a49f 100644
--- a/drivers/virtio/virtio_input.c
+++ b/drivers/virtio/virtio_input.c
@@ -30,7 +30,7 @@ static void virtinput_queue_evtbuf(struct virtio_input *vi,
 	struct scatterlist sg[1];
 
 	sg_init_one(sg, evtbuf, sizeof(*evtbuf));
-	virtqueue_add_inbuf(vi->evt, sg, 1, evtbuf, GFP_ATOMIC);
+	virtqueue_add_inbuf_cache_clean(vi->evt, sg, 1, evtbuf, GFP_ATOMIC);
 }
 
 static void virtinput_recv_events(struct virtqueue *vq)
-- 
MST