netdev - Re: [PATCH v2 08/15] vsock/virtio: use virtqueue_add_inbuf_cache

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Message-ID: <aV-6UTKChBhiTynA@sgarzare-redhat>
Date: Thu, 8 Jan 2026 15:08:31 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, 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>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Petr Tesarik <ptesarik@...e.com>, Leon Romanovsky <leon@...nel.org>, 
	Jason Gunthorpe <jgg@...pe.ca>, Bartosz Golaszewski <brgl@...nel.org>, 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: Re: [PATCH v2 08/15] vsock/virtio: use
 virtqueue_add_inbuf_cache_clean for events

On Mon, Jan 05, 2026 at 03:23:21AM -0500, Michael S. Tsirkin wrote:
>The event_list array contains 8 small (4-byte) 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.
>
>The previous patch isolated event_list in its own cache lines
>so the warnings are spurious.
>
>Use virtqueue_add_inbuf_cache_clean() to indicate that the CPU does not
>write into these fields, suppressing the warnings.
>
>Reported-by: Cong Wang <xiyou.wangcong@...il.com>
>Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>---
> net/vmw_vsock/virtio_transport.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

Acked-by: Stefano Garzarella <sgarzare@...hat.com>

>
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index bb94baadfd8b..ef983c36cb66 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -392,7 +392,7 @@ static int virtio_vsock_event_fill_one(struct virtio_vsock *vsock,
>
> 	sg_init_one(&sg, event, sizeof(*event));
>
>-	return virtqueue_add_inbuf(vq, &sg, 1, event, GFP_KERNEL);
>+	return virtqueue_add_inbuf_cache_clean(vq, &sg, 1, event, GFP_KERNEL);
> }
>
> /* event_lock must be held */
>-- 
>MST
>