From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
To: Paolo Abeni <pabeni@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org, virtualization@lists.linux.dev
Subject: Re: [PATCH vhost v3 0/4] virtio_net: rx enable premapped mode by default
Date: Sun, 28 Apr 2024 09:18:49 +0800 [thread overview]
Message-ID: <1714267129.6438966-2-xuanzhuo@linux.alibaba.com> (raw)
In-Reply-To: <45002f120a57ec362459868a67af1627a22274d1.camel@redhat.com>
On Fri, 26 Apr 2024 13:00:08 +0200, Paolo Abeni <pabeni@redhat.com> wrote:
> On Wed, 2024-04-24 at 16:16 +0800, Xuan Zhuo wrote:
> > Actually, for the virtio drivers, we can enable premapped mode whatever
> > the value of use_dma_api. Because we provide the virtio dma apis.
> > So the driver can enable premapped mode unconditionally.
> >
> > This patch set makes the big mode of virtio-net to support premapped mode.
> > And enable premapped mode for rx by default.
> >
> > Based on the following points, we do not use page pool to manage these
> > pages:
> >
> > 1. virtio-net uses the DMA APIs wrapped by virtio core. Therefore,
> > we can only prevent the page pool from performing DMA operations, and
> > let the driver perform DMA operations on the allocated pages.
> > 2. But when the page pool releases the page, we have no chance to
> > execute dma unmap.
> > 3. A solution to #2 is to execute dma unmap every time before putting
> > the page back to the page pool. (This is actually a waste, we don't
> > execute unmap so frequently.)
> > 4. But there is another problem, we still need to use page.dma_addr to
> > save the dma address. Using page.dma_addr while using page pool is
> > unsafe behavior.
> > 5. And we need space the chain the pages submitted once to virtio core.
> >
> > More:
> > https://lore.kernel.org/all/CACGkMEu=Aok9z2imB_c5qVuujSh=vjj1kx12fy9N7hqyi+M5Ow@mail.gmail.com/
> >
> > Why we do not use the page space to store the dma?
> > http://lore.kernel.org/all/CACGkMEuyeJ9mMgYnnB42=hw6umNuo=agn7VBqBqYPd7GN=+39Q@mail.gmail.com
> >
> > Please review.
> >
> > v3:
> > 1. big mode still use the mode that virtio core does the dma map/unmap
> >
> > v2:
> > 1. make gcc happy in page_chain_get_dma()
> > http://lore.kernel.org/all/202404221325.SX5ChRGP-lkp@intel.com
> >
> > v1:
> > 1. discussed for using page pool
> > 2. use dma sync to replace the unmap for the first page
>
> Judging by the subj prefix, this is targeting the vhost tree, right?
>
> There are a few patches landing on virtio_net on net-next, I guess
> there will be some conflict while pushing to Linux (but I haven't
> double check yet!)
>
> Perhaps you could provide a stable git branch so that both vhost and
> netdev could pull this set?
This patch set is related with the virio core, so I push this
to the vhost branch. And there is no new feature to the virtio-net.
Similar situation in the past, we pushed to the vhost branch.
I am ok to net-next or vhost. We can hear others
@Michael
Thanks.
>
> Thanks!
>
> Paolo
>
prev parent reply other threads:[~2024-04-28 1:32 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-24 8:16 [PATCH vhost v3 0/4] virtio_net: rx enable premapped mode by default Xuan Zhuo
2024-04-24 8:16 ` [PATCH vhost v3 1/4] virtio_ring: enable premapped mode whatever use_dma_api Xuan Zhuo
2024-04-24 8:16 ` [PATCH vhost v3 2/4] virtio_net: big mode skip the unmap check Xuan Zhuo
2024-04-25 2:11 ` Jason Wang
2024-04-25 2:35 ` Xuan Zhuo
2024-04-25 6:04 ` Jason Wang
2024-04-24 8:16 ` [PATCH vhost v3 3/4] virtio_net: rx remove premapped failover code Xuan Zhuo
2024-04-24 8:16 ` [PATCH vhost v3 4/4] virtio_net: remove the misleading comment Xuan Zhuo
2024-04-26 11:00 ` [PATCH vhost v3 0/4] virtio_net: rx enable premapped mode by default Paolo Abeni
2024-04-28 1:18 ` Xuan Zhuo [this message]
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