Re: [GIT PULL] virtio: features

[Michael Roth <michael.roth@amd.com>]

On Wed, Sep 27, 2023 at 09:47:39AM +0800, Xuan Zhuo wrote:
> On Tue, 26 Sep 2023 08:04:51 -0500, Michael Roth <michael.roth@amd.com> wrote:
> > On Sun, Sep 03, 2023 at 06:13:38PM -0400, Michael S. Tsirkin wrote:
> > > The following changes since commit 2dde18cd1d8fac735875f2e4987f11817cc0bc2c:
> > >
> > >   Linux 6.5 (2023-08-27 14:49:51 -0700)
> > >
> > > are available in the Git repository at:
> > >
> > >   https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git tags/for_linus
> > >
> > > for you to fetch changes up to 1acfe2c1225899eab5ab724c91b7e1eb2881b9ab:
> > >
> > >   virtio_ring: fix avail_wrap_counter in virtqueue_add_packed (2023-09-03 18:10:24 -0400)
> > >
> > > ----------------------------------------------------------------
> > > virtio: features
> > >
> > > a small pull request this time around, mostly because the
> > > vduse network got postponed to next relase so we can be sure
> > > we got the security store right.
> > >
> > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > >
> > > ----------------------------------------------------------------
> > > Eugenio P閞ez (4):
> > >       vdpa: add VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK flag
> > >       vdpa: accept VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK backend feature
> > >       vdpa: add get_backend_features vdpa operation
> > >       vdpa_sim: offer VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK
> > >
> > > Jason Wang (1):
> > >       virtio_vdpa: build affinity masks conditionally
> > >
> > > Xuan Zhuo (12):
> > >       virtio_ring: check use_dma_api before unmap desc for indirect
> > >       virtio_ring: put mapping error check in vring_map_one_sg
> > >       virtio_ring: introduce virtqueue_set_dma_premapped()
> > >       virtio_ring: support add premapped buf
> > >       virtio_ring: introduce virtqueue_dma_dev()
> > >       virtio_ring: skip unmap for premapped
> > >       virtio_ring: correct the expression of the description of virtqueue_resize()
> > >       virtio_ring: separate the logic of reset/enable from virtqueue_resize
> > >       virtio_ring: introduce virtqueue_reset()
> > >       virtio_ring: introduce dma map api for virtqueue
> > >       virtio_ring: introduce dma sync api for virtqueue
> > >       virtio_net: merge dma operations when filling mergeable buffers
> >
> > This ^ patch (upstream commit 295525e29a) seems to cause a
> > network-related regression when using SWIOTLB in the guest. I noticed
> > this initially testing SEV guests, which use SWIOTLB by default, but
> > it can also be seen with normal guests when forcing SWIOTLB via
> > swiotlb=force kernel cmdline option. I see it with both 6.6-rc1 and
> > 6.6-rc2 (haven't tried rc3 yet, but don't see any related changes
> > there), and reverting 714073495f seems to avoid the issue.
> >
> > Steps to reproduce:
> >
> > 1) Boot QEMU/KVM guest with 6.6-rc2 with swiotlb=force via something like the following cmdline:
> >
> >    qemu-system-x86_64 \
> >    -machine q35 -smp 4,maxcpus=255 -cpu EPYC-Milan-v2 \
> >    -enable-kvm -m 16G,slots=5,maxmem=256G -vga none \
> >    -device virtio-scsi-pci,id=scsi0,disable-legacy=on,iommu_platform=true \
> >    -drive file=/home/mroth/storage/ubuntu-18.04-seves2.qcow2,if=none,id=drive0,snapshot=off \
> >    -device scsi-hd,id=hd0,drive=drive0,bus=scsi0.0 \
> >    -device virtio-net-pci,netdev=netdev0,id=net0,disable-legacy=on,iommu_platform=true,romfile= \
> >    -netdev tap,script=/home/mroth/qemu-ifup,id=netdev0 \
> >    -L /home/mroth/storage/AMDSEV2/snp-release-2023-09-23/usr/local/share/qemu \
> >    -drive if=pflash,format=raw,unit=0,file=/home/mroth/storage/AMDSEV2/snp-release-2023-09-23/usr/local/share/qemu/OVMF_CODE.fd,readonly \
> >    -drive if=pflash,format=raw,unit=1,file=/home/mroth/storage/AMDSEV2/snp-release-2023-09-23/usr/local/share/qemu/OVMF_VARS.fd \
> >    -debugcon file:debug.log -global isa-debugcon.iobase=0x402 -msg timestamp=on \
> >    -kernel /boot/vmlinuz-6.6.0-rc2-vanilla0+ \
> >    -initrd /boot/initrd.img-6.6.0-rc2-vanilla0+ \
> >    -append "root=UUID=d72a6d1c-06cf-4b79-af43-f1bac4f620f9 ro console=ttyS0,115200n8 earlyprintk=serial,ttyS0,115200 debug=1 sev=debug page_poison=0 spec_rstack_overflow=off swiotlb=force"
> >
> > 2) scp a small file from the host to the guest IP via its virtio-net device.
> >    Smaller file sizes succeed, but the larger the file the more likely
> >    it will fail. e.g.:
> >
> >    mroth@host:~$ dd if=/dev/zero of=test bs=1K count=19
> >    19+0 records in
> >    19+0 records out
> >    19456 bytes (19 kB, 19 KiB) copied, 0.000940134 s, 20.7 MB/s
> >    mroth@host:~$ scp test vm0:
> >    test                                                                    100%   19KB  10.1MB/s   00:00
> >    mroth@host:~$ dd if=/dev/zero of=test bs=1K count=20
> >    20+0 records in
> >    20+0 records out
> >    20480 bytes (20 kB, 20 KiB) copied, 0.00093774 s, 21.8 MB/s
> >    mroth@host:~$ scp test vm0:
> >    test                                                                      0%    0     0.0KB/s   --:-- ETA
> >    client_loop: send disconnect: Broken pipe
> >    lost connection
> >    mroth@host:~$
> 
> 
> Hi Michael,
> 
> Thanks for the report.
> 
> Cloud you try this fix?  I reproduce this issue, and that works for me.

Hello,

This seems to resolve the issue for me.

Thanks for the quick fix.

-Mike

> Thanks.
> 
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 98dc9b49d56b..9ece27dc5144 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -589,16 +589,16 @@ static void virtnet_rq_unmap(struct receive_queue *rq, void *buf, u32 len)
> 
>         --dma->ref;
> 
> -       if (dma->ref) {
> -               if (dma->need_sync && len) {
> -                       offset = buf - (head + sizeof(*dma));
> +       if (dma->need_sync && len) {
> +               offset = buf - (head + sizeof(*dma));
> 
> -                       virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr, offset,
> -                                                               len, DMA_FROM_DEVICE);
> -               }
> +               virtqueue_dma_sync_single_range_for_cpu(rq->vq, dma->addr,
> +                                                       offset, len,
> +                                                       DMA_FROM_DEVICE);
> +       }
> 
> +       if (dma->ref)
>                 return;
> -       }
> 
>         virtqueue_dma_unmap_single_attrs(rq->vq, dma->addr, dma->len,
>                                          DMA_FROM_DEVICE, DMA_ATTR_SKIP_CPU_SYNC);
> 
> 
> >
> > Thanks,
> >
> > Mike
> >
> > >
> > > Yuan Yao (1):
> > >       virtio_ring: fix avail_wrap_counter in virtqueue_add_packed
> > >
> > > Yue Haibing (1):
> > >       vdpa/mlx5: Remove unused function declarations
> > >
> > >  drivers/net/virtio_net.c           | 230 ++++++++++++++++++---
> > >  drivers/vdpa/mlx5/core/mlx5_vdpa.h |   3 -
> > >  drivers/vdpa/vdpa_sim/vdpa_sim.c   |   8 +
> > >  drivers/vhost/vdpa.c               |  15 +-
> > >  drivers/virtio/virtio_ring.c       | 412 ++++++++++++++++++++++++++++++++-----
> > >  drivers/virtio/virtio_vdpa.c       |  17 +-
> > >  include/linux/vdpa.h               |   4 +
> > >  include/linux/virtio.h             |  22 ++
> > >  include/uapi/linux/vhost_types.h   |   4 +
> > >  9 files changed, 625 insertions(+), 90 deletions(-)
> > >