| Message ID | 20240424081636.124029-1-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | virtio_net: rx enable premapped mode by default | expand |
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? Thanks! Paolo
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 >
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 Thanks. Xuan Zhuo (4): virtio_ring: enable premapped mode whatever use_dma_api virtio_net: big mode skip the unmap check virtio_net: rx remove premapped failover code virtio_net: remove the misleading comment drivers/net/virtio_net.c | 90 +++++++++++++++--------------------- drivers/virtio/virtio_ring.c | 7 +-- 2 files changed, 38 insertions(+), 59 deletions(-) -- 2.32.0.3.g01195cf9f