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Subject: Re: [PATCH v9 2/7] virtio-pmem: Add virtio pmem driver
To:     Pankaj Gupta <pagupta@redhat.com>, linux-nvdimm@lists.01.org,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-acpi@vger.kernel.org,
        qemu-devel@nongnu.org, linux-ext4@vger.kernel.org,
        linux-xfs@vger.kernel.org, mst@redhat.com
Cc:     dan.j.williams@intel.com, zwisler@kernel.org,
        vishal.l.verma@intel.com, dave.jiang@intel.com,
        jasowang@redhat.com, willy@infradead.org, rjw@rjwysocki.net,
        hch@infradead.org, lenb@kernel.org, jack@suse.cz, tytso@mit.edu,
        adilger.kernel@dilger.ca, darrick.wong@oracle.com,
        lcapitulino@redhat.com, kwolf@redhat.com, imammedo@redhat.com,
        jmoyer@redhat.com, nilal@redhat.com, riel@surriel.com,
        stefanha@redhat.com, aarcange@redhat.com, david@fromorbit.com,
        cohuck@redhat.com, xiaoguangrong.eric@gmail.com,
        pbonzini@redhat.com, kilobyte@angband.pl, yuval.shaia@oracle.com,
        jstaron@google.com
References: <20190514145422.16923-1-pagupta@redhat.com>
 <20190514145422.16923-3-pagupta@redhat.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <9f6b1d8e-ef90-7d8b-56da-61a426953ba3@redhat.com>
Date:   Wed, 15 May 2019 22:46:00 +0200
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Sender: linux-ext4-owner@vger.kernel.org
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> +	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;
}

#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