On Fri, Jan 28, 2022 at 7:00 AM Jason Wang <jasow...@redhat.com> wrote:
>
>
> 在 2022/1/22 上午4:27, Eugenio Pérez 写道:
> > Vhost shadow virtqueue (SVQ) is an intermediate jump for virtqueue
> > notifications and buffers, allowing qemu to track them. While qemu is
> > forwarding the buffers and virtqueue changes, it is able to commit the
> > memory it's being dirtied, the same way regular qemu's VirtIO devices
> > do.
> >
> > This commit only exposes basic SVQ allocation and free. Next patches of
> > the series add functionality like notifications and buffers forwarding.
> >
> > Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> > ---
> > hw/virtio/vhost-shadow-virtqueue.h | 21 ++++++++++
> > hw/virtio/vhost-shadow-virtqueue.c | 64 ++++++++++++++++++++++++++++++
> > hw/virtio/meson.build | 2 +-
> > 3 files changed, 86 insertions(+), 1 deletion(-)
> > create mode 100644 hw/virtio/vhost-shadow-virtqueue.h
> > create mode 100644 hw/virtio/vhost-shadow-virtqueue.c
> >
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.h
> > b/hw/virtio/vhost-shadow-virtqueue.h
> > new file mode 100644
> > index 0000000000..61ea112002
> > --- /dev/null
> > +++ b/hw/virtio/vhost-shadow-virtqueue.h
> > @@ -0,0 +1,21 @@
> > +/*
> > + * vhost shadow virtqueue
> > + *
> > + * SPDX-FileCopyrightText: Red Hat, Inc. 2021
> > + * SPDX-FileContributor: Author: Eugenio Pérez <epere...@redhat.com>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#ifndef VHOST_SHADOW_VIRTQUEUE_H
> > +#define VHOST_SHADOW_VIRTQUEUE_H
> > +
> > +#include "hw/virtio/vhost.h"
> > +
> > +typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
> > +
> > +VhostShadowVirtqueue *vhost_svq_new(void);
> > +
> > +void vhost_svq_free(VhostShadowVirtqueue *vq);
> > +
> > +#endif
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.c
> > b/hw/virtio/vhost-shadow-virtqueue.c
> > new file mode 100644
> > index 0000000000..5ee7b401cb
> > --- /dev/null
> > +++ b/hw/virtio/vhost-shadow-virtqueue.c
> > @@ -0,0 +1,64 @@
> > +/*
> > + * vhost shadow virtqueue
> > + *
> > + * SPDX-FileCopyrightText: Red Hat, Inc. 2021
> > + * SPDX-FileContributor: Author: Eugenio Pérez <epere...@redhat.com>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "hw/virtio/vhost-shadow-virtqueue.h"
> > +
> > +#include "qemu/error-report.h"
> > +#include "qemu/event_notifier.h"
> > +
> > +/* Shadow virtqueue to relay notifications */
> > +typedef struct VhostShadowVirtqueue {
> > + /* Shadow kick notifier, sent to vhost */
> > + EventNotifier hdev_kick;
> > + /* Shadow call notifier, sent to vhost */
> > + EventNotifier hdev_call;
> > +} VhostShadowVirtqueue;
> > +
> > +/**
> > + * Creates vhost shadow virtqueue, and instruct vhost device to use the
> > shadow
> > + * methods and file descriptors.
> > + */
> > +VhostShadowVirtqueue *vhost_svq_new(void)
> > +{
> > + g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1);
> > + int r;
> > +
> > + r = event_notifier_init(&svq->hdev_kick, 0);
> > + if (r != 0) {
> > + error_report("Couldn't create kick event notifier: %s",
> > + strerror(errno));
> > + goto err_init_hdev_kick;
> > + }
> > +
> > + r = event_notifier_init(&svq->hdev_call, 0);
> > + if (r != 0) {
> > + error_report("Couldn't create call event notifier: %s",
> > + strerror(errno));
> > + goto err_init_hdev_call;
> > + }
> > +
> > + return g_steal_pointer(&svq);
> > +
> > +err_init_hdev_call:
> > + event_notifier_cleanup(&svq->hdev_kick);
> > +
> > +err_init_hdev_kick:
> > + return NULL;
> > +}
> > +
> > +/**
> > + * Free the resources of the shadow virtqueue.
> > + */
> > +void vhost_svq_free(VhostShadowVirtqueue *vq)
> > +{
> > + event_notifier_cleanup(&vq->hdev_kick);
> > + event_notifier_cleanup(&vq->hdev_call);
> > + g_free(vq);
> > +}
> > diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build
> > index 521f7d64a8..2dc87613bc 100644
> > --- a/hw/virtio/meson.build
> > +++ b/hw/virtio/meson.build
> > @@ -11,7 +11,7 @@ softmmu_ss.add(when: 'CONFIG_ALL', if_true:
> > files('vhost-stub.c'))
> >
> > virtio_ss = ss.source_set()
> > virtio_ss.add(files('virtio.c'))
> > -virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c',
> > 'vhost-backend.c'))
> > +virtio_ss.add(when: 'CONFIG_VHOST', if_true: files('vhost.c',
> > 'vhost-backend.c', 'vhost-shadow-virtqueue.c'))
>
>
> I wonder if we need a dedicated config option for shadow virtqueue.
>
I'd say that the changes are isolated enough and require no external
library dependencies so the gain is little. But it can be done with an
explicit enable/disable for sure.
Thanks!
> Thanks
>
>
> > virtio_ss.add(when: 'CONFIG_VHOST_USER', if_true: files('vhost-user.c'))
> > virtio_ss.add(when: 'CONFIG_VHOST_VDPA', if_true: files('vhost-vdpa.c'))
> > virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true:
> > files('virtio-balloon.c'))
>
