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[80.230.85.71]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49260e14d0asm23280535e9.0.2026.06.24.00.08.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2026 00:08:26 -0700 (PDT) Date: Wed, 24 Jun 2026 03:08:24 -0400 From: "Michael S. Tsirkin" To: Longjun Tang Cc: xuanzhuo@linux.alibaba.com, jasowang@redhat.com, edumazet@google.com, virtualization@lists.linux.dev, netdev@vger.kernel.org, tanglongjun@kylinos.cn Subject: Re: [PATCH v3] virtio_net: disable cb when NAPI is busy-polled Message-ID: <20260624030656-mutt-send-email-mst@kernel.org> References: <20260624070206.85467-1-lange_tang@163.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20260624070206.85467-1-lange_tang@163.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: jHzwWCsoF_kCdnYuG9PRXYxwfxHxL2PJNgwcW7IF6c0_1782284909 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Jun 24, 2026 at 03:02:06PM +0800, Longjun Tang wrote: > From: Longjun Tang > > When busy-poll is active, napi_schedule_prep() returns false in > virtqueue_napi_schedule(), so virtqueue_disable_cb() is skipped. > The device may keep firing irqs until reaches virtqueue_napi_complete(). > Under load (received == budget), it will lead to a large number > of spurious interrupts. > > Fix it by disabling the callback at the virtnet_poll() entry. This keeps > the callback off while we poll and re-enable and it is re-enabled > by virtqueue_napi_complete() > when going idle. > > Fixes: ceef438d613f ("virtio_net: remove custom busy_poll") > Acked-by: Michael S. Tsirkin > Signed-off-by: Longjun Tang > > --- > V1 -> V2: Remain agnostic to busy polling > V2 -> V3: Add fixes tag > --- > drivers/net/virtio_net.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index f4adcfee7a80..0a11f2b32500 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -3008,6 +3008,11 @@ static int virtnet_poll(struct napi_struct *napi, int budget) > unsigned int xdp_xmit = 0; > bool napi_complete; > > + /* Keep callbacks suppressed for the duration of this poll, > + * busy-poll need. I don't know what "busy-poll need" means. Just drop this part? In fact, the whole comment can go, we know virtqueue_disable_cb disables callbacks. > + */ > + virtqueue_disable_cb(rq->vq); > + > virtnet_poll_cleantx(rq, budget); > > received = virtnet_receive(rq, budget, &xdp_xmit); > -- > 2.43.0