Re: [RFC PATCH for 8.0] backends/vhost-user: relax the ioeventfd check
On Fri, 2 Dec 2022 at 08:23, Alex Bennée wrote:
>
> While you certainly need ioeventfds to work for KVM guests it
> shouldn't be limited to that. We can run vhost-user backends for TCG
> guests and either use ioeventfds or in band signalling.
I suggest tweaking this sentence so it's clear that you mean QEMU's
simulated eventfds rather than kvm.ko's real ioeventfds:
s/use eventfds or in band signalling/simulate ioeventfds or use in
band signalling/
>
> Maybe we should apply the same fix as b0aa77d36d (vhost-user: fix
> ioeventfd_enabled)?
>
> With this change I can run:
>
> $QEMU $OPTS \
> -display gtk,gl=on \
> -device vhost-user-gpu-pci,chardev=vhgpu \
> -chardev socket,id=vhgpu,path=vhgpu.sock
>
> with:
>
> ./contrib/vhost-user-gpu/vhost-user-gpu \
> -s vhgpu.sock \
> -v
>
> and at least see things start-up (although the display gets rotated by
> 180 degrees).
>
> Signed-off-by: Alex Bennée
> ---
> backends/vhost-user.c | 10 ++
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> index 5dedb2d987..87d43fb03a 100644
> --- a/backends/vhost-user.c
> +++ b/backends/vhost-user.c
> @@ -21,12 +21,6 @@
> #include "io/channel-command.h"
> #include "hw/virtio/virtio-bus.h"
>
> -static bool
> -ioeventfd_enabled(void)
> -{
> -return kvm_enabled() && kvm_eventfds_enabled();
> -}
> -
> int
> vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> unsigned nvqs, Error **errp)
> @@ -35,8 +29,8 @@ vhost_user_backend_dev_init(VhostUserBackend *b,
> VirtIODevice *vdev,
>
> assert(!b->vdev && vdev);
>
> -if (!ioeventfd_enabled()) {
> -error_setg(errp, "vhost initialization failed: requires kvm");
> +if (kvm_enabled() && !kvm_eventfds_enabled()) {
> +error_setg(errp, "vhost initialization failed: kvm required
> ioeventfds");
> return -1;
> }
The check can be dropped completely. If kvm.ko doesn't support
ioeventfds QEMU can simulate them just like it does with TCG. In
practice I don't think this happens with a reasonably modern kernel
version.
Stefan
Re: [RFC PATCH for 8.0] backends/vhost-user: relax the ioeventfd check
On Mon, Dec 19, 2022 at 05:48:50PM +, Alex Bennée wrote:
>
> Alex Bennée writes:
>
> > While you certainly need ioeventfds to work for KVM guests it
> > shouldn't be limited to that. We can run vhost-user backends for TCG
> > guests and either use ioeventfds or in band signalling.
> >
> > Maybe we should apply the same fix as b0aa77d36d (vhost-user: fix
> > ioeventfd_enabled)?
> >
> > With this change I can run:
> >
> > $QEMU $OPTS \
> > -display gtk,gl=on \
> > -device vhost-user-gpu-pci,chardev=vhgpu \
> > -chardev socket,id=vhgpu,path=vhgpu.sock
> >
> > with:
> >
> > ./contrib/vhost-user-gpu/vhost-user-gpu \
> > -s vhgpu.sock \
> > -v
> >
> > and at least see things start-up (although the display gets rotated by
> > 180 degrees).
> >
> > Signed-off-by: Alex Bennée
> > ---
> > backends/vhost-user.c | 10 ++
> > 1 file changed, 2 insertions(+), 8 deletions(-)
> >
> > diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> > index 5dedb2d987..87d43fb03a 100644
> > --- a/backends/vhost-user.c
> > +++ b/backends/vhost-user.c
> > @@ -21,12 +21,6 @@
> > #include "io/channel-command.h"
> > #include "hw/virtio/virtio-bus.h"
> >
> > -static bool
> > -ioeventfd_enabled(void)
> > -{
> > -return kvm_enabled() && kvm_eventfds_enabled();
> > -}
> > -
> > int
> > vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> > unsigned nvqs, Error **errp)
> > @@ -35,8 +29,8 @@ vhost_user_backend_dev_init(VhostUserBackend *b,
> > VirtIODevice *vdev,
> >
> > assert(!b->vdev && vdev);
> >
> > -if (!ioeventfd_enabled()) {
> > -error_setg(errp, "vhost initialization failed: requires kvm");
> > +if (kvm_enabled() && !kvm_eventfds_enabled()) {
> > +error_setg(errp, "vhost initialization failed: kvm required
> > ioeventfds");
> > return -1;
> > }
>
> Gentle ping?
>
Yea why not. Pls post a non RFC patch.
--
MST
Re: [RFC PATCH for 8.0] backends/vhost-user: relax the ioeventfd check
Alex Bennée writes:
> While you certainly need ioeventfds to work for KVM guests it
> shouldn't be limited to that. We can run vhost-user backends for TCG
> guests and either use ioeventfds or in band signalling.
>
> Maybe we should apply the same fix as b0aa77d36d (vhost-user: fix
> ioeventfd_enabled)?
>
> With this change I can run:
>
> $QEMU $OPTS \
> -display gtk,gl=on \
> -device vhost-user-gpu-pci,chardev=vhgpu \
> -chardev socket,id=vhgpu,path=vhgpu.sock
>
> with:
>
> ./contrib/vhost-user-gpu/vhost-user-gpu \
> -s vhgpu.sock \
> -v
>
> and at least see things start-up (although the display gets rotated by
> 180 degrees).
>
> Signed-off-by: Alex Bennée
> ---
> backends/vhost-user.c | 10 ++
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> index 5dedb2d987..87d43fb03a 100644
> --- a/backends/vhost-user.c
> +++ b/backends/vhost-user.c
> @@ -21,12 +21,6 @@
> #include "io/channel-command.h"
> #include "hw/virtio/virtio-bus.h"
>
> -static bool
> -ioeventfd_enabled(void)
> -{
> -return kvm_enabled() && kvm_eventfds_enabled();
> -}
> -
> int
> vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
> unsigned nvqs, Error **errp)
> @@ -35,8 +29,8 @@ vhost_user_backend_dev_init(VhostUserBackend *b,
> VirtIODevice *vdev,
>
> assert(!b->vdev && vdev);
>
> -if (!ioeventfd_enabled()) {
> -error_setg(errp, "vhost initialization failed: requires kvm");
> +if (kvm_enabled() && !kvm_eventfds_enabled()) {
> +error_setg(errp, "vhost initialization failed: kvm required
> ioeventfds");
> return -1;
> }
Gentle ping?
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
