Re: [Qemu-devel] [PATCH v9 2/7] virtio-pmem: Add virtio pmem driver

[David Hildenbrand]

On 15.05.19 22:46, David Hildenbrand wrote:
>> +    vpmem->vdev = vdev;
>> +    vdev->priv = vpmem;
>> +    err = init_vq(vpmem);
>> +    if (err) {
>> +            dev_err(&vdev->dev, "failed to initialize virtio pmem vq's\n");
>> +            goto out_err;
>> +    }
>> +
>> +    virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>> +                    start, &vpmem->start);
>> +    virtio_cread(vpmem->vdev, struct virtio_pmem_config,
>> +                    size, &vpmem->size);
>> +
>> +    res.start = vpmem->start;
>> +    res.end   = vpmem->start + vpmem->size-1;
> 
> nit: " - 1;"
> 
>> +    vpmem->nd_desc.provider_name = "virtio-pmem";
>> +    vpmem->nd_desc.module = THIS_MODULE;
>> +
>> +    vpmem->nvdimm_bus = nvdimm_bus_register(&vdev->dev,
>> +                                            &vpmem->nd_desc);
>> +    if (!vpmem->nvdimm_bus) {
>> +            dev_err(&vdev->dev, "failed to register device with 
>> nvdimm_bus\n");
>> +            err = -ENXIO;
>> +            goto out_vq;
>> +    }
>> +
>> +    dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus);
>> +
>> +    ndr_desc.res = &res;
>> +    ndr_desc.numa_node = nid;
>> +    ndr_desc.flush = async_pmem_flush;
>> +    set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
>> +    set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
>> +    nd_region = nvdimm_pmem_region_create(vpmem->nvdimm_bus, &ndr_desc);
>> +    if (!nd_region) {
>> +            dev_err(&vdev->dev, "failed to create nvdimm region\n");
>> +            err = -ENXIO;
>> +            goto out_nd;
>> +    }
>> +    nd_region->provider_data = dev_to_virtio(nd_region->dev.parent->parent);
>> +    return 0;
>> +out_nd:
>> +    nvdimm_bus_unregister(vpmem->nvdimm_bus);
>> +out_vq:
>> +    vdev->config->del_vqs(vdev);
>> +out_err:
>> +    return err;
>> +}
>> +
>> +static void virtio_pmem_remove(struct virtio_device *vdev)
>> +{
>> +    struct nvdimm_bus *nvdimm_bus = dev_get_drvdata(&vdev->dev);
>> +
>> +    nvdimm_bus_unregister(nvdimm_bus);
>> +    vdev->config->del_vqs(vdev);
>> +    vdev->config->reset(vdev);
>> +}
>> +
>> +static struct virtio_driver virtio_pmem_driver = {
>> +    .driver.name            = KBUILD_MODNAME,
>> +    .driver.owner           = THIS_MODULE,
>> +    .id_table               = id_table,
>> +    .probe                  = virtio_pmem_probe,
>> +    .remove                 = virtio_pmem_remove,
>> +};
>> +
>> +module_virtio_driver(virtio_pmem_driver);
>> +MODULE_DEVICE_TABLE(virtio, id_table);
>> +MODULE_DESCRIPTION("Virtio pmem driver");
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h
>> new file mode 100644
>> index 000000000000..ab1da877575d
>> --- /dev/null
>> +++ b/drivers/nvdimm/virtio_pmem.h
>> @@ -0,0 +1,60 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * virtio_pmem.h: virtio pmem Driver
>> + *
>> + * Discovers persistent memory range information
>> + * from host and provides a virtio based flushing
>> + * interface.
>> + **/
>> +
>> +#ifndef _LINUX_VIRTIO_PMEM_H
>> +#define _LINUX_VIRTIO_PMEM_H
>> +
>> +#include <linux/virtio_ids.h>
>> +#include <linux/module.h>
>> +#include <linux/virtio_config.h>
>> +#include <uapi/linux/virtio_pmem.h>
>> +#include <linux/libnvdimm.h>
>> +#include <linux/spinlock.h>
>> +
>> +struct virtio_pmem_request {
>> +    /* Host return status corresponding to flush request */
>> +    int ret;
>> +
>> +    /* command name*/
>> +    char name[16];
> 
> So ... why are we sending string commands and expect native-endianess
> integers and don't define a proper request/response structure + request
> types in include/uapi/linux/virtio_pmem.h like
> 
> struct virtio_pmem_resp {
>       __virtio32 ret;
> }

FWIW, I wonder if we should even properly translate return values and
define types like

VIRTIO_PMEM_RESP_TYPE_OK        0
VIRTIO_PMEM_RESP_TYPE_EIO       1

..

> 
> #define VIRTIO_PMEM_REQ_TYPE_FLUSH    1
> struct virtio_pmem_req {
>       __virtio16 type;
> }
> 
> ... and this way we also define a proper endianess format for exchange
> and keep it extensible
> 
> @MST, what's your take on this?
> 
> 


-- 

Thanks,

David / dhildenb