Re: [PATCH vhost v3 00/19] virtio: drivers maintain dma info for premapped vq

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Thu, 29 Feb 2024 03:21:14 -0500, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Thu, Feb 29, 2024 at 03:20:25PM +0800, Xuan Zhuo wrote:
> > As discussed:
> > http://lore.kernel.org/all/CACGkMEvq0No8QGC46U4mGsMtuD44fD_cfLcPaVmJ3rHYqRZxYg@mail.gmail.com
> >
> > If the virtio is premapped mode, the driver should manage the dma info by self.
> > So the virtio core should not store the dma info.
> > So we can release the memory used to store the dma info.
> >
> > But if the desc_extra has not dma info, we face a new question,
> > it is hard to get the dma info of the desc with indirect flag.
> > For split mode, that is easy from desc, but for the packed mode,
> > it is hard to get the dma info from the desc. And for hardening
> > the dma unmap is saft, we should store the dma info of indirect
> > descs.
> >
> > So I introduce the "structure the indirect desc table" to
> > allocate space to store dma info with the desc table.
> >
> > On the other side, we mix the descs with indirect flag
> > with other descs together to share the unmap api. That
> > is complex. I found if we we distinguish the descs with
> > VRING_DESC_F_INDIRECT before unmap, thing will be clearer.
> >
> > Because of the dma array is allocated in the find_vqs(),
> > so I introduce a new parameter to find_vqs().
> >
> > Note:
> >     this is on the top of
> >         [PATCH vhost v1] virtio: packed: fix unmap leak for indirect desc table
> >         http://lore.kernel.org/all/20240223071833.26095-1-xuanzhuo@linux.alibaba.com
> >
> > Please review.
> >
> > Thanks
> >
> > v3:
> >     1. fix the conflict with the vp_modern_create_avq().
>
> Okay but are you going to address huge memory waste all this is causing for
> - people who never do zero copy
> - systems where dma unmap is a nop
>
> ?
>
> You should address all comments when you post a new version, not just
> what was expedient, or alternatively tag patch as RFC and explain
> in commit log that you plan to do it later.


Do you miss this one?
http://lore.kernel.org/all/1708997579.5613105-1-xuanzhuo@linux.alibaba.com

I asked you. But I didnot recv your answer.

Thanks.


>
> > v2:
> >     1. change the dma item of virtio-net, every item have MAX_SKB_FRAGS + 2
> >         addr + len pairs.
> >     2. introduce virtnet_sq_free_stats for __free_old_xmit
> >
> > v1:
> >     1. rename transport_vq_config to vq_transport_config
> >     2. virtio-net set dma meta number to (ring-size + 1)(MAX_SKB_FRGAS +2)
> >     3. introduce virtqueue_dma_map_sg_attrs
> >     4. separate vring_create_virtqueue to an independent commit
> >
> >
> >
> > Xuan Zhuo (19):
> >   virtio_ring: introduce vring_need_unmap_buffer
> >   virtio_ring: packed: remove double check of the unmap ops
> >   virtio_ring: packed: structure the indirect desc table
> >   virtio_ring: split: remove double check of the unmap ops
> >   virtio_ring: split: structure the indirect desc table
> >   virtio_ring: no store dma info when unmap is not needed
> >   virtio: find_vqs: pass struct instead of multi parameters
> >   virtio: vring_create_virtqueue: pass struct instead of multi
> >     parameters
> >   virtio: vring_new_virtqueue(): pass struct instead of multi parameters
> >   virtio_ring: simplify the parameters of the funcs related to
> >     vring_create/new_virtqueue()
> >   virtio: find_vqs: add new parameter premapped
> >   virtio_ring: export premapped to driver by struct virtqueue
> >   virtio_net: set premapped mode by find_vqs()
> >   virtio_ring: remove api of setting vq premapped
> >   virtio_ring: introduce dma map api for page
> >   virtio_ring: introduce virtqueue_dma_map_sg_attrs
> >   virtio_net: unify the code for recycling the xmit ptr
> >   virtio_net: rename free_old_xmit_skbs to free_old_xmit
> >   virtio_net: sq support premapped mode
> >
> >  arch/um/drivers/virtio_uml.c             |  31 +-
> >  drivers/net/virtio_net.c                 | 283 ++++++---
> >  drivers/platform/mellanox/mlxbf-tmfifo.c |  24 +-
> >  drivers/remoteproc/remoteproc_virtio.c   |  31 +-
> >  drivers/s390/virtio/virtio_ccw.c         |  33 +-
> >  drivers/virtio/virtio_mmio.c             |  30 +-
> >  drivers/virtio/virtio_pci_common.c       |  59 +-
> >  drivers/virtio/virtio_pci_common.h       |   9 +-
> >  drivers/virtio/virtio_pci_legacy.c       |  16 +-
> >  drivers/virtio/virtio_pci_modern.c       |  38 +-
> >  drivers/virtio/virtio_ring.c             | 698 ++++++++++++-----------
> >  drivers/virtio/virtio_vdpa.c             |  45 +-
> >  include/linux/virtio.h                   |  13 +-
> >  include/linux/virtio_config.h            |  48 +-
> >  include/linux/virtio_ring.h              |  82 +--
> >  tools/virtio/virtio_test.c               |   4 +-
> >  tools/virtio/vringh_test.c               |  28 +-
> >  17 files changed, 847 insertions(+), 625 deletions(-)
> >
> > --
> > 2.32.0.3.g01195cf9f
>