RE: [PATCH v2 04/10] vdpa-dev: implement the instance_init/class_init interface

[longpeng2--- via <qemu-devel@nongnu.org>]

> -----Original Message-----
> From: Stefano Garzarella [mailto:sgarzare@redhat.com]
> Sent: Monday, March 7, 2022 4:10 PM
> To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
> <longpeng2@huawei.com>
> Cc: stefanha@redhat.com; mst@redhat.com; cohuck@redhat.com;
> pbonzini@redhat.com; Gonglei (Arei) <arei.gonglei@huawei.com>; Yechuan
> <yechuan@huawei.com>; Huangzhichao <huangzhichao@huawei.com>;
> qemu-devel@nongnu.org
> Subject: Re: [PATCH v2 04/10] vdpa-dev: implement the instance_init/class_init
> interface
> 
> Hi Longpeng,
> 
> On Sat, Mar 05, 2022 at 06:06:42AM +0000, Longpeng (Mike, Cloud Infrastructure
> Service Product Dept.) wrote:
> >Hi Stefano,
> >
> >> -----Original Message-----
> >> From: Stefano Garzarella [mailto:sgarzare@redhat.com]
> >> Sent: Wednesday, January 19, 2022 7:24 PM
> >> To: Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
> >> <longpeng2@huawei.com>
> >> Cc: stefanha@redhat.com; mst@redhat.com; cohuck@redhat.com;
> >> pbonzini@redhat.com; Gonglei (Arei) <arei.gonglei@huawei.com>; Yechuan
> >> <yechuan@huawei.com>; Huangzhichao <huangzhichao@huawei.com>;
> >> qemu-devel@nongnu.org
> >> Subject: Re: [PATCH v2 04/10] vdpa-dev: implement the
> instance_init/class_init
> >> interface
> >>
> >> On Mon, Jan 17, 2022 at 08:43:25PM +0800, Longpeng(Mike) via wrote:
> >> >From: Longpeng <longpeng2@huawei.com>
> >> >
> >> >Implements the .instance_init and the .class_init interface.
> >> >
> >> >Signed-off-by: Longpeng <longpeng2@huawei.com>
> >> >---
> >> > hw/virtio/vdpa-dev-pci.c     | 52 ++++++++++++++++++++++-
> >> > hw/virtio/vdpa-dev.c         | 81 +++++++++++++++++++++++++++++++++++-
> >> > include/hw/virtio/vdpa-dev.h |  5 +++
> >> > 3 files changed, 134 insertions(+), 4 deletions(-)
> >> >
> >> >diff --git a/hw/virtio/vdpa-dev-pci.c b/hw/virtio/vdpa-dev-pci.c
> >> >index a5a7b528a9..257538dbdd 100644
> >> >--- a/hw/virtio/vdpa-dev-pci.c
> >> >+++ b/hw/virtio/vdpa-dev-pci.c
> >> >@@ -25,12 +25,60 @@ struct VhostVdpaDevicePCI {
> >> >
> >> > static void vhost_vdpa_device_pci_instance_init(Object *obj)
> >> > {
> >> >-    return;
> >> >+    VhostVdpaDevicePCI *dev = VHOST_VDPA_DEVICE_PCI(obj);
> >> >+
> >> >+    virtio_instance_init_common(obj, &dev->vdev, sizeof(dev->vdev),
> >> >+                                TYPE_VHOST_VDPA_DEVICE);
> >> >+    object_property_add_alias(obj, "bootindex", OBJECT(&dev->vdev),
> >> >+                              "bootindex");
> >> >+}
> >> >+
> >> >+static Property vhost_vdpa_device_pci_properties[] = {
> >> >+    DEFINE_PROP_END_OF_LIST(),
> >> >+};
> >> >+
> >> >+static void
> >> >+vhost_vdpa_device_pci_realize(VirtIOPCIProxy *vpci_dev, Error **errp)
> >> >+{
> >> >+    VhostVdpaDevicePCI *dev = VHOST_VDPA_DEVICE_PCI(vpci_dev);
> >> >+    DeviceState *vdev = DEVICE(&dev->vdev);
> >> >+    uint32_t vdev_id;
> >> >+    uint32_t num_queues;
> >> >+    int fd;
> >> >+
> >> >+    fd = qemu_open(dev->vdev.vdpa_dev, O_RDWR, errp);
> >>
> >> We should use `vdpa_dev_fd` if the user set it, and I think we should
> >> also check that `vdpa_dev` is not null.
> >>
> >
> >The user can set both 'vdpa_dev_fd' and 'vdpa_dev' now, but how
> >to make sure the 'vdpa_dev_fd' is really a FD of the 'vdpa_dev' ?
> >Maybe we should remove 'vdpa_dev_fd' from
> >'vhost_vdpa_device_properties',
> >so the user can only set 'vdpa_dev'.
> 
> This is the same problem that would happen if the user passed a path any
> file or device (e.g. /dev/null). I believe that on the first operation
> on it (e.g. an ioctl) we would get an error and exit.
> 

Yes, but how about the 'vdpa_dev_fd' refers to /dev/vhost-vdpa-0 but
the 'vdpa_dev' refers to /dev/vhost-vdpa-1 ? Should we need to consider
this case ?

> I think we should allow to specify an fd (as we already do for other
> vhost devices), because it's a common use case when qemu is launched
> from higher layers (e.g. libvirt).
> 
> >
> >> >+    if (*errp) {
> >> >+        return;
> >> >+    }
> >> >+
> >> >+    vdev_id = vhost_vdpa_device_get_u32(fd, VHOST_VDPA_GET_DEVICE_ID,
> errp);
> >> >+    if (*errp) {
> >> >+        qemu_close(fd);
> >> >+        return;
> >> >+    }
> >> >+
> >> >+    num_queues = vhost_vdpa_device_get_u32(fd, VHOST_VDPA_GET_VQS_NUM,
> >> errp);
> >>                                                   ^
> >> The build fails here, I think this should be VHOST_VDPA_GET_VQS_COUNT
> >>
> >
> >Yes, I sent a wrong version, I'll send v3 later.
> 
> Thanks,
> Stefano