Re: [RFC PATCH for 8.1 2/6] vdpa: add vhost_vdpa_reset_status_fd

[Eugenio Perez Martin]

On Wed, Mar 22, 2023 at 3:24 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Fri, Mar 17, 2023 at 03:55:38PM +0100, Eugenio Pérez wrote:
> >This allows to reset a vhost-vdpa device from external subsystems like
> >vhost-net.  It is used in subsequent patches to negotiate features and
> >probe for CVQ ASID isolation.
> >
> >Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> >---
> > include/hw/virtio/vhost-vdpa.h |  1 +
> > hw/virtio/vhost-vdpa.c         | 58 +++++++++++++++++++++++-----------
> > 2 files changed, 41 insertions(+), 18 deletions(-)
> >
> >diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> >index c278a2a8de..28de7da91e 100644
> >--- a/include/hw/virtio/vhost-vdpa.h
> >+++ b/include/hw/virtio/vhost-vdpa.h
> >@@ -54,6 +54,7 @@ typedef struct vhost_vdpa {
> >     VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
> > } VhostVDPA;
> >
> >+void vhost_vdpa_reset_status_fd(int fd);
> > int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range 
> > *iova_range);
> >
> > int vhost_vdpa_dma_map(struct vhost_vdpa *v, uint32_t asid, hwaddr iova,
> >diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> >index bbabea18f3..7a2053b8d9 100644
> >--- a/hw/virtio/vhost-vdpa.c
> >+++ b/hw/virtio/vhost-vdpa.c
> >@@ -335,38 +335,45 @@ static const MemoryListener vhost_vdpa_memory_listener 
> >= {
> >     .region_del = vhost_vdpa_listener_region_del,
> > };
> >
> >-static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
> >-                             void *arg)
> >+static int vhost_vdpa_dev_fd(const struct vhost_dev *dev)
>
> What is the purpose of this refactoring?
> I guess, since vhost_net does not have `struct vhost_dev *` we want to
> use fd directly?
>

Right.

> It might be better to split this patch into two.
>

Do you mean to create vhost_vdpa_dev_fd first and then users?

> > {
> >     struct vhost_vdpa *v = dev->opaque;
> >-    int fd = v->device_fd;
> >-    int ret;
> >
> >     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
> >+    return v->device_fd;
> >+}
> >+
> >+static int vhost_vdpa_call_fd(int fd, unsigned long int request, void *arg)
> >+{
> >+    int ret = ioctl(fd, request, arg);
> >
> >-    ret = ioctl(fd, request, arg);
> >     return ret < 0 ? -errno : ret;
> > }
> >
> >-static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
> >+static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
> >+                           void *arg)
> >+{
> >+    return vhost_vdpa_call_fd(vhost_vdpa_dev_fd(dev), request, arg);
> >+}
> >+
> >+static int vhost_vdpa_add_status_fd(int fd, uint8_t status)
> > {
> >     uint8_t s;
> >     int ret;
> >
> >-    trace_vhost_vdpa_add_status(dev, status);
> >-    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> >+    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
> >     if (ret < 0) {
> >         return ret;
> >     }
> >
> >     s |= status;
> >
> >-    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &s);
> >+    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &s);
> >     if (ret < 0) {
> >         return ret;
> >     }
> >
> >-    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_STATUS, &s);
> >+    ret = vhost_vdpa_call_fd(fd, VHOST_VDPA_GET_STATUS, &s);
> >     if (ret < 0) {
> >         return ret;
> >     }
> >@@ -378,6 +385,12 @@ static int vhost_vdpa_add_status(struct vhost_dev *dev, 
> >uint8_t status)
> >     return 0;
> > }
> >
> >+static int vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
> >+{
> >+    trace_vhost_vdpa_add_status(dev, status);
> >+    return vhost_vdpa_add_status_fd(vhost_vdpa_dev_fd(dev), status);
> >+}
> >+
> > int vhost_vdpa_get_iova_range(int fd, struct vhost_vdpa_iova_range 
> > *iova_range)
> > {
> >     int ret = ioctl(fd, VHOST_VDPA_GET_IOVA_RANGE, iova_range);
> >@@ -709,16 +722,20 @@ static int vhost_vdpa_get_device_id(struct vhost_dev 
> >*dev,
> >     return ret;
> > }
> >
> >+static int vhost_vdpa_reset_device_fd(int fd)
> >+{
> >+    uint8_t status = 0;
> >+
> >+    return vhost_vdpa_call_fd(fd, VHOST_VDPA_SET_STATUS, &status);
> >+}
> >+
> > static int vhost_vdpa_reset_device(struct vhost_dev *dev)
> > {
> >     struct vhost_vdpa *v = dev->opaque;
> >-    int ret;
> >-    uint8_t status = 0;
> >
> >-    ret = vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &status);
> >-    trace_vhost_vdpa_reset_device(dev);
> >     v->suspended = false;
>
> I think it is pre-existing, but if VHOST_VDPA_SET_STATUS fails,
> should we set anyway `v->suspended = false`?
>

It's a good question. I think the most correct is to keep as the
previous value, but I'm not sure if reset is actually allowed to fail.

Thanks!