Jason Wang wrote:
> The NVDIMM region could be available before the virtio_device_ready()
> that is called by virtio_dev_probe(). This means the driver tries to
> use device before DRIVER_OK which violates the spec, fixing this by
> set device ready before the nvdimm_pmem_region_create().
Can you clarify the failure path. What race is virtio_device_ready()
losing?
>
> Note that this means the virtio_pmem_host_ack() could be triggered
> before the creation of the nd region, this is safe since the
> virtio_pmem_host_ack() since pmem_lock has been initialized and we
> check if we've added any buffer before trying to proceed.
I got a little bit lost with the usage of "we" here. Can you clarify
which function / context is making which guarantee?
>
> Fixes 6e84200c0a29 ("virtio-pmem: Add virtio pmem driver")
> Signed-off-by: Jason Wang <[email protected]>
> ---
> drivers/nvdimm/virtio_pmem.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> index 48f8327d0431..173f2f5adaea 100644
> --- a/drivers/nvdimm/virtio_pmem.c
> +++ b/drivers/nvdimm/virtio_pmem.c
> @@ -84,6 +84,17 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> ndr_desc.provider_data = vdev;
> set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
> + /*
> + * The NVDIMM region could be available before the
> + * virtio_device_ready() that is called by
> + * virtio_dev_probe(), so we set device ready here.
> + *
> + * The callback - virtio_pmem_host_ack() is safe to be called
> + * before the nvdimm_pmem_region_create() since the pmem_lock
> + * has been initialized and legality of a used buffer is
> + * validated before moving forward.
This comment feels like changelog material. Just document why
virtio_device_ready() must be called before device_add() of the
nd_region.
> + */
> + virtio_device_ready(vdev);
> nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
> if (!nd_region) {
> dev_err(&vdev->dev, "failed to create nvdimm region\n");
> @@ -92,6 +103,7 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
> }
> return 0;
> out_nd:
> + virtio_reset_device(vdev);
> nvdimm_bus_unregister(vpmem->nvdimm_bus);
> out_vq:
> vdev->config->del_vqs(vdev);
> --
> 2.25.1
>
