[v6,3/4] vhost-vdpa: uAPI to resume the device
Commit Message
From: Sebastien Boeuf <sebastien.boeuf@intel.com>
This new ioctl adds support for resuming the device from userspace.
This is required when trying to restore the device in a functioning
state after it's been suspended. It is already possible to reset a
suspended device, but that means the device must be reconfigured and
all the IOMMU/IOTLB mappings must be recreated. This new operation
allows the device to be resumed without going through a full reset.
This is particularly useful when trying to perform offline migration of
a virtual machine (also known as snapshot/restore) as it allows the VMM
to resume the virtual machine back to a running state after the snapshot
is performed.
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
---
drivers/vhost/vdpa.c | 18 ++++++++++++++++++
include/uapi/linux/vhost.h | 8 ++++++++
2 files changed, 26 insertions(+)
Comments
On Tue, Jan 03, 2023 at 11:51:07AM +0100, sebastien.boeuf@intel.com wrote:
>From: Sebastien Boeuf <sebastien.boeuf@intel.com>
>
>This new ioctl adds support for resuming the device from userspace.
>
>This is required when trying to restore the device in a functioning
>state after it's been suspended. It is already possible to reset a
>suspended device, but that means the device must be reconfigured and
>all the IOMMU/IOTLB mappings must be recreated. This new operation
>allows the device to be resumed without going through a full reset.
>
>This is particularly useful when trying to perform offline migration of
>a virtual machine (also known as snapshot/restore) as it allows the VMM
>to resume the virtual machine back to a running state after the snapshot
>is performed.
>
>Acked-by: Jason Wang <jasowang@redhat.com>
>Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
>---
> drivers/vhost/vdpa.c | 18 ++++++++++++++++++
> include/uapi/linux/vhost.h | 8 ++++++++
> 2 files changed, 26 insertions(+)
>
>diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>index 833617d00ef6..1db7bd39fb63 100644
>--- a/drivers/vhost/vdpa.c
>+++ b/drivers/vhost/vdpa.c
>@@ -502,6 +502,21 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
> return ops->suspend(vdpa);
> }
>
>+/* After a successful return of this ioctl the device resumes processing
>+ * virtqueue descriptors. The device becomes fully operational the same way it
>+ * was before it was suspended.
>+ */
>+static long vhost_vdpa_resume(struct vhost_vdpa *v)
>+{
>+ struct vdpa_device *vdpa = v->vdpa;
>+ const struct vdpa_config_ops *ops = vdpa->config;
>+
>+ if (!ops->resume)
>+ return -EOPNOTSUPP;
>+
>+ return ops->resume(vdpa);
>+}
>+
> static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> void __user *argp)
> {
>@@ -687,6 +702,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> case VHOST_VDPA_SUSPEND:
> r = vhost_vdpa_suspend(v);
> break;
>+ case VHOST_VDPA_RESUME:
>+ r = vhost_vdpa_resume(v);
>+ break;
> default:
> r = vhost_dev_ioctl(&v->vdev, cmd, argp);
> if (r == -ENOIOCTLCMD)
>diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>index f9f115a7c75b..92e1b700b51c 100644
>--- a/include/uapi/linux/vhost.h
>+++ b/include/uapi/linux/vhost.h
>@@ -180,4 +180,12 @@
> */
> #define VHOST_VDPA_SUSPEND _IO(VHOST_VIRTIO, 0x7D)
>
>+/* Resume a device so it can resume processing virtqueue requests
>+ *
>+ * After the return of this ioctl the device will have restored all the
>+ * necessary states and it is fully operational to continue processing the
>+ * virtqueue descriptors.
IIUC this is a no-op if the device wasn't suspended.
If you have to resend, maybe add this info also here in the user
documentation.
Anyway, the patch LGTM:
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>+ */
>+#define VHOST_VDPA_RESUME _IO(VHOST_VIRTIO, 0x7E)
>+
> #endif
>--
>2.37.2
>
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@@ -502,6 +502,21 @@ static long vhost_vdpa_suspend(struct vhost_vdpa *v)
return ops->suspend(vdpa);
}
+/* After a successful return of this ioctl the device resumes processing
+ * virtqueue descriptors. The device becomes fully operational the same way it
+ * was before it was suspended.
+ */
+static long vhost_vdpa_resume(struct vhost_vdpa *v)
+{
+ struct vdpa_device *vdpa = v->vdpa;
+ const struct vdpa_config_ops *ops = vdpa->config;
+
+ if (!ops->resume)
+ return -EOPNOTSUPP;
+
+ return ops->resume(vdpa);
+}
+
static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
void __user *argp)
{
@@ -687,6 +702,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
case VHOST_VDPA_SUSPEND:
r = vhost_vdpa_suspend(v);
break;
+ case VHOST_VDPA_RESUME:
+ r = vhost_vdpa_resume(v);
+ break;
default:
r = vhost_dev_ioctl(&v->vdev, cmd, argp);
if (r == -ENOIOCTLCMD)
@@ -180,4 +180,12 @@
*/
#define VHOST_VDPA_SUSPEND _IO(VHOST_VIRTIO, 0x7D)
+/* Resume a device so it can resume processing virtqueue requests
+ *
+ * After the return of this ioctl the device will have restored all the
+ * necessary states and it is fully operational to continue processing the
+ * virtqueue descriptors.
+ */
+#define VHOST_VDPA_RESUME _IO(VHOST_VIRTIO, 0x7E)
+
#endif