linux-ext4 - Re: [PATCH v9 2/7] virtio-pmem: Add virtio pmem driver

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Date:   Thu, 16 May 2019 03:54:15 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-acpi@...r.kernel.org,
        qemu-devel@...gnu.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, mst@...hat.com,
        dan j williams <dan.j.williams@...el.com>,
        zwisler@...nel.org, vishal l verma <vishal.l.verma@...el.com>,
        dave jiang <dave.jiang@...el.com>, jasowang@...hat.com,
        willy@...radead.org, rjw@...ysocki.net, hch@...radead.org,
        lenb@...nel.org, jack@...e.cz, tytso@....edu,
        adilger kernel <adilger.kernel@...ger.ca>,
        darrick wong <darrick.wong@...cle.com>, lcapitulino@...hat.com,
        kwolf@...hat.com, imammedo@...hat.com, jmoyer@...hat.com,
        nilal@...hat.com, riel@...riel.com, stefanha@...hat.com,
        aarcange@...hat.com, david@...morbit.com, cohuck@...hat.com,
        xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
        pbonzini@...hat.com, kilobyte@...band.pl,
        yuval shaia <yuval.shaia@...cle.com>, jstaron@...gle.com
Subject: Re: [PATCH v9 2/7] virtio-pmem: Add virtio pmem driver


> >> +	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

Don't think these are required as only failure and success
return types easy to understand.

Thanks,
Pankaj
> 
> ..
> 
> > 
> > #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
>