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Subject: Re: [PATCH 15/52] fuse: map virtio_fs DAX window BAR
To:     Vivek Goyal <vgoyal@redhat.com>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     miklos@szeredi.hu, stefanha@redhat.com, dgilbert@redhat.com,
        sweil@redhat.com, swhiteho@redhat.com,
        Cornelia Huck <cohuck@redhat.com>,
        Halil Pasic <pasic@linux.ibm.com>
References: <20181210171318.16998-1-vgoyal@redhat.com>
 <20181210171318.16998-16-vgoyal@redhat.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
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Date:   Wed, 12 Dec 2018 17:37:35 +0100
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On 10.12.2018 18:12, Vivek Goyal wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>

> +static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> +{
> +	struct virtio_fs_memremap_info *mi;
> +	struct dev_pagemap *pgmap;
> +	struct pci_dev *pci_dev;
> +	phys_addr_t phys_addr;
> +	size_t len;
> +	int ret;
> +
> +	if (!IS_ENABLED(CONFIG_DAX_DRIVER))
> +		return 0;
> +
> +	/* HACK implement VIRTIO shared memory regions instead of
> +	 * directly accessing the PCI BAR from a virtio device driver.
> +	 */
> +	pci_dev = container_of(vdev->dev.parent, struct pci_dev, dev);
> +
> +	/* TODO Is this safe - the virtio_pci_* driver doesn't use managed
> +	 * device APIs? */
> +	ret = pcim_enable_device(pci_dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* TODO handle case where device doesn't expose BAR? */
> +	ret = pci_request_region(pci_dev, VIRTIO_FS_WINDOW_BAR,
> +				 "virtio-fs-window");
> +	if (ret < 0) {
> +		dev_err(&vdev->dev, "%s: failed to request window BAR\n",
> +			__func__);
> +		return ret;
> +	}

Can we please have a generic virtio interface to map the address (the default can then
fall back to PCI) instead of mapping a PCI bar? This would make it easier to implement
virtio-ccw or virtio-mmio.