Re: [PATCH v3] media: add virtio-media driver

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Em Wed, 18 Jun 2025 23:16:47 +0900
"Alexandre Courbot" <gnurou@gmail.com> escreveu:

> Hi Mauro,
> 
> On Tue Jun 17, 2025 at 5:49 PM JST, Mauro Carvalho Chehab wrote:
> > Hi Alex,
> >
> > Em Tue, 27 May 2025 23:03:39 +0900
> > Alexandre Courbot <gnurou@gmail.com> escreveu:
> >  
> >> > > > Btw, I was looking at:
> >> > > >
> >> > > >         https://github.com/chromeos/virtio-media
> >> > > >
> >> > > > (I'm assuming that this is the QEMU counterpart, right?)    
> >> > >
> >> > > crosvm actually, but QEMU support is also being worked on.    
> >> >
> >> > Do you have already QEMU patches? The best is to have the Kernel driver
> >> > submitted altogether with QEMU, as Kernel developers need it to do the
> >> > tests. In my case, I never use crosvm, and I don't have any Chromebook
> >> > anymore.    
> >> 
> >> IIRC Albert Esteve was working on this, maybe he can share the current status.  
> >
> > Any news regards to it?  
> 
> Albert shared the latest status. There is one in-flight patch series
> required in qemu [1], and then this branch of vhost-device should
> contain the necessary support [2]. Albert is waiting for the virtio spec
> to get merged before sending a pull request IIUC.
> 
> [1] https://patchew.org/QEMU/20250217164012.246727-1-aesteve@redhat.com/
> [2] https://github.com/aesteve-rh/vhost-device/tree/virtio-media
> 
> >  
> >> Note that crosvm does not require a Chromebook, you can build and run
> >> it pretty easily on a regular PC. I have put together a document to
> >> help with that:
> >> 
> >> https://github.com/chromeos/virtio-media/blob/main/TRY_IT_OUT.md  
> >
> > I started looking on it today. Already installed crossvm (I had to
> > install libcap-devel to build it). Still, I'm not familiar with
> > crossvm, which is a little be painful. In particular, how can I
> > enable network on it and speedup it?  
> 
> There is a "./tools/examples/setup_network" in the crosvm repository that
> will setup a TAP device. Once this is done, you can pass the "--net
> tap-name=crosvm_tap" argument to crosvm, and the network device should
> be visible and usable.
> 
> Let me reply to the rest of your questions in your latest mail, with the
> most recent logs.

Heh, I just managed to get it work maybe 10 minutes before your e-mail...

I'm building crossvm with:

	cargo build --release --features  "gpu,media,virgl_renderer,x"

To also have GPU working.

Network setup required a rather complex script to set it up without
breaking my ssh section with the machine where I'm running crossvm.

In case you need, I'm enclosing it.

Now, I need to allocate another time slot for tests and review.

---

#!/bin/bash

PHY=enp0s25
BRIDGE=crossvm_br
TAP=crossvm_tap

IP_MASK=$(ip -br addr show $PHY | awk '{print $3}' | grep -oE '^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/[0-9]+')
if [ -z "$IP_MASK" ]; then
  echo "Failed to detect IP address on $PHY. Exiting."
  exit 1
fi

GW=$(ip -br route show default dev $PHY | awk '{print $3}')
if [ -z "$GW" ]; then
  echo "Failed to detect default gateway on $PHY. Exiting."
  exit 1
fi

restore_network() {
  echo "Restoring original network config on $PHY..."
  sudo ip link set dev $BRIDGE down || true
  sudo ip link del $BRIDGE || true
  sudo ip link set dev $TAP down || true
  sudo ip tuntap del dev $TAP mode tap || true

  sudo ip addr flush dev $PHY
  sudo ip addr add ${IP_MASK} dev $PHY
  sudo ip link set dev $PHY up
  sudo ip route add default via $GW
}

if ! lsmod | grep -q '^bridge'; then
    sudo modprobe bridge
fi

trap 'catch $LINENO "$BASH_COMMAND"' ERR

catch() {
    echo "Error on line $1: $2"
    restore_network
    exit 1
}

if ip link show $TAP &>/dev/null; then
  echo "Removing existing tap $TAP"
  sudo ip link set dev $TAP down
  sudo ip tuntap del dev $TAP mode tap
fi

if ip link show $BRIDGE &>/dev/null; then
  echo "Removing existing bridge $BRIDGE"
  sudo ip link set dev $BRIDGE down
  sudo ip link del $BRIDGE
fi

# Create bridge device
sudo ip link add name $BRIDGE type bridge
sudo ip link set dev $BRIDGE up
sudo ip link set dev $BRIDGE type bridge forward_delay 0

# Add physical interface to bridge
sudo ip link set dev $PHY master $BRIDGE

# Create tap device
sudo ip tuntap add dev $TAP mode tap
sudo ip link set dev $TAP up

# Add tap to bridge
sudo ip link set dev $TAP master $BRIDGE

# Get an address to the bridge
sudo dhclient $BRIDGE

# Start crossvm

sudo ./crosvm/target/release/crosvm run \
  linux/arch/x86/boot/bzImage \
  -c 4 -m size=4096 \
  --disable-sandbox \
  --block debian-12.img \
  -p "root=/dev/vda1" \
  --v4l2-proxy /dev/video0 \
  --gpu backend=virglrenderer \
  --net tap-name=crossvm_tap,vhost-net