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Message-ID: <20240906061055-mutt-send-email-mst@kernel.org>
Date: Fri, 6 Sep 2024 06:12:35 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: 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, Si-Wei Liu <si-wei.liu@...cle.com>,
Darren Kenny <darren.kenny@...cle.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Eugenio Pérez <eperezma@...hat.com>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH v2 5/7] Revert "virtio_net: rx remove premapped
failover code"
On Fri, Sep 06, 2024 at 06:02:50PM +0800, Xuan Zhuo wrote:
> On Fri, 6 Sep 2024 05:52:36 -0400, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > This reverts commit defd28aa5acb0fd7c15adc6bc40a8ac277d04dea.
> >
> > leads to crashes with no ACCESS_PLATFORM when
> > sysctl net.core.high_order_alloc_disable=1
> >
> > Cc: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > Reported-by: Si-Wei Liu <si-wei.liu@...cle.com>
> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> > ---
> > drivers/net/virtio_net.c | 89 +++++++++++++++++++++++-----------------
> > 1 file changed, 52 insertions(+), 37 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 0944430dfb1f..0a2ec9570521 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -348,6 +348,9 @@ struct receive_queue {
> >
> > /* Record the last dma info to free after new pages is allocated. */
> > struct virtnet_rq_dma *last_dma;
> > +
> > + /* Do dma by self */
> > + bool do_dma;
> > };
> >
> > /* This structure can contain rss message with maximum settings for indirection table and keysize
> > @@ -867,7 +870,7 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
> > void *buf;
> >
> > buf = virtqueue_get_buf_ctx(rq->vq, len, ctx);
> > - if (buf)
> > + if (buf && rq->do_dma)
> > virtnet_rq_unmap(rq, buf, *len);
> >
> > return buf;
> > @@ -880,6 +883,11 @@ static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
> > u32 offset;
> > void *head;
> >
> > + if (!rq->do_dma) {
> > + sg_init_one(rq->sg, buf, len);
> > + return;
> > + }
> > +
> > head = page_address(rq->alloc_frag.page);
> >
> > offset = buf - head;
> > @@ -905,42 +913,44 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> >
> > head = page_address(alloc_frag->page);
> >
> > - dma = head;
> > + if (rq->do_dma) {
> > + dma = head;
> >
> > - /* new pages */
> > - if (!alloc_frag->offset) {
> > - if (rq->last_dma) {
> > - /* Now, the new page is allocated, the last dma
> > - * will not be used. So the dma can be unmapped
> > - * if the ref is 0.
> > + /* new pages */
> > + if (!alloc_frag->offset) {
> > + if (rq->last_dma) {
> > + /* Now, the new page is allocated, the last dma
> > + * will not be used. So the dma can be unmapped
> > + * if the ref is 0.
> > + */
> > + virtnet_rq_unmap(rq, rq->last_dma, 0);
> > + rq->last_dma = NULL;
> > + }
> > +
> > + dma->len = alloc_frag->size - sizeof(*dma);
> > +
> > + addr = virtqueue_dma_map_single_attrs(rq->vq, dma + 1,
> > + dma->len, DMA_FROM_DEVICE, 0);
> > + if (virtqueue_dma_mapping_error(rq->vq, addr))
> > + return NULL;
> > +
> > + dma->addr = addr;
> > + dma->need_sync = virtqueue_dma_need_sync(rq->vq, addr);
> > +
> > + /* Add a reference to dma to prevent the entire dma from
> > + * being released during error handling. This reference
> > + * will be freed after the pages are no longer used.
> > */
> > - virtnet_rq_unmap(rq, rq->last_dma, 0);
> > - rq->last_dma = NULL;
> > + get_page(alloc_frag->page);
> > + dma->ref = 1;
> > + alloc_frag->offset = sizeof(*dma);
> > +
> > + rq->last_dma = dma;
> > }
> >
> > - dma->len = alloc_frag->size - sizeof(*dma);
> > -
> > - addr = virtqueue_dma_map_single_attrs(rq->vq, dma + 1,
> > - dma->len, DMA_FROM_DEVICE, 0);
> > - if (virtqueue_dma_mapping_error(rq->vq, addr))
> > - return NULL;
> > -
> > - dma->addr = addr;
> > - dma->need_sync = virtqueue_dma_need_sync(rq->vq, addr);
> > -
> > - /* Add a reference to dma to prevent the entire dma from
> > - * being released during error handling. This reference
> > - * will be freed after the pages are no longer used.
> > - */
> > - get_page(alloc_frag->page);
> > - dma->ref = 1;
> > - alloc_frag->offset = sizeof(*dma);
> > -
> > - rq->last_dma = dma;
> > + ++dma->ref;
> > }
> >
> > - ++dma->ref;
> > -
> > buf = head + alloc_frag->offset;
> >
> > get_page(alloc_frag->page);
> > @@ -957,9 +967,12 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > if (!vi->mergeable_rx_bufs && vi->big_packets)
> > return;
> >
> > - for (i = 0; i < vi->max_queue_pairs; i++)
> > - /* error should never happen */
> > - BUG_ON(virtqueue_set_dma_premapped(vi->rq[i].vq));
> > + for (i = 0; i < vi->max_queue_pairs; i++) {
> > + if (virtqueue_set_dma_premapped(vi->rq[i].vq))
> > + continue;
> > +
> > + vi->rq[i].do_dma = true;
> > + }
>
> This is too much code to revert. We can just revert this and next one.
> And add a patch to turn off the default premapped setting (return from this
> function directly). Otherwise, we will have to do all the work again in the
> future.
>
> There is no need to revert xsk related code, xsk function cannot be enabled, in
> the case that premapped mode is not turned on. There is no direct impact itself.
>
> Thanks.
I tried but quickly got lost as the automatic
revert did not work, and it's very close to release, so
I wanted to be sure it's right.
Post your own version of a revert for testing then please.
>
> > }
> >
> > static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
> > @@ -2107,7 +2120,8 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
> >
> > err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> > if (err < 0) {
> > - virtnet_rq_unmap(rq, buf, 0);
> > + if (rq->do_dma)
> > + virtnet_rq_unmap(rq, buf, 0);
> > put_page(virt_to_head_page(buf));
> > }
> >
> > @@ -2221,7 +2235,8 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
> > ctx = mergeable_len_to_ctx(len + room, headroom);
> > err = virtqueue_add_inbuf_ctx(rq->vq, rq->sg, 1, buf, ctx, gfp);
> > if (err < 0) {
> > - virtnet_rq_unmap(rq, buf, 0);
> > + if (rq->do_dma)
> > + virtnet_rq_unmap(rq, buf, 0);
> > put_page(virt_to_head_page(buf));
> > }
> >
> > @@ -5392,7 +5407,7 @@ static void free_receive_page_frags(struct virtnet_info *vi)
> > int i;
> > for (i = 0; i < vi->max_queue_pairs; i++)
> > if (vi->rq[i].alloc_frag.page) {
> > - if (vi->rq[i].last_dma)
> > + if (vi->rq[i].do_dma && vi->rq[i].last_dma)
> > virtnet_rq_unmap(&vi->rq[i], vi->rq[i].last_dma, 0);
> > put_page(vi->rq[i].alloc_frag.page);
> > }
> > --
> > MST
> >
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