linux-kernel - Re: [PATCH 18/52] virtio-fs: Map cache using the values from the capabilities

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Message-ID: <de46a955-813b-355d-49f2-4d866603a8fa@redhat.com>
Date:   Thu, 13 Dec 2018 10:10:10 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Vivek Goyal <vgoyal@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     miklos@...redi.hu, stefanha@...hat.com, dgilbert@...hat.com,
        sweil@...hat.com, swhiteho@...hat.com
Subject: Re: [PATCH 18/52] virtio-fs: Map cache using the values from the
 capabilities

On 10.12.18 18:12, Vivek Goyal wrote:
> Instead of assuming we had the fixed bar for the cache, use the
> value from the capabilities.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@...hat.com>
> ---
>  fs/fuse/virtio_fs.c | 32 +++++++++++++++++---------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 60d496c16841..55bac1465536 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -14,11 +14,6 @@
>  #include <uapi/linux/virtio_pci.h>
>  #include "fuse_i.h"
>  
> -enum {
> -	/* PCI BAR number of the virtio-fs DAX window */
> -	VIRTIO_FS_WINDOW_BAR = 2,
> -};
> -
>  /* List of virtio-fs device instances and a lock for the list */
>  static DEFINE_MUTEX(virtio_fs_mutex);
>  static LIST_HEAD(virtio_fs_instances);
> @@ -518,7 +513,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
>  	struct dev_pagemap *pgmap;
>  	struct pci_dev *pci_dev;
>  	phys_addr_t phys_addr;
> -	size_t len;
> +	size_t bar_len;
>  	int ret;
>  	u8 have_cache, cache_bar;
>  	u64 cache_offset, cache_len;
> @@ -551,17 +546,13 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
>          }
>  
>  	/* TODO handle case where device doesn't expose BAR? */

For virtio-pmem we decided to not go via BARs as this would effectively
make it only usable for virtio-pci implementers. Instead, we are going
to export the applicable physical device region directly (e.g.
phys_start, phys_size in virtio config), so it is decoupled from PCI
details. Doing the same for virtio-fs would allow e.g. also virtio-ccw
to make eventually use of this.

> -	ret = pci_request_region(pci_dev, VIRTIO_FS_WINDOW_BAR,
> -				 "virtio-fs-window");
> +	ret = pci_request_region(pci_dev, cache_bar, "virtio-fs-window");
>  	if (ret < 0) {
>  		dev_err(&vdev->dev, "%s: failed to request window BAR\n",
>  			__func__);
>  		return ret;
>  	}
>  
> -	phys_addr = pci_resource_start(pci_dev, VIRTIO_FS_WINDOW_BAR);
> -	len = pci_resource_len(pci_dev, VIRTIO_FS_WINDOW_BAR);
> -
>  	mi = devm_kzalloc(&pci_dev->dev, sizeof(*mi), GFP_KERNEL);
>  	if (!mi)
>  		return -ENOMEM;
> @@ -586,6 +577,17 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
>  	pgmap->ref = &mi->ref;
>  	pgmap->type = MEMORY_DEVICE_FS_DAX;
>  
> +	phys_addr = pci_resource_start(pci_dev, cache_bar);
> +	bar_len = pci_resource_len(pci_dev, cache_bar);
> +
> +	if (cache_offset + cache_len > bar_len) {
> +		dev_err(&vdev->dev,
> +			"%s: cache bar shorter than cap offset+len\n",
> +			__func__);
> +		return -EINVAL;
> +	}
> +	phys_addr += cache_offset;
> +
>  	/* Ideally we would directly use the PCI BAR resource but
>  	 * devm_memremap_pages() wants its own copy in pgmap.  So
>  	 * initialize a struct resource from scratch (only the start
> @@ -594,7 +596,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
>  	pgmap->res = (struct resource){
>  		.name = "virtio-fs dax window",
>  		.start = phys_addr,
> -		.end = phys_addr + len,
> +		.end = phys_addr + cache_len,
>  	};
>  
>  	fs->window_kaddr = devm_memremap_pages(&pci_dev->dev, pgmap);
> @@ -607,10 +609,10 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
>  		return ret;
>  
>  	fs->window_phys_addr = phys_addr;
> -	fs->window_len = len;
> +	fs->window_len = cache_len;
>  
> -	dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len %zu\n",
> -		__func__, fs->window_kaddr, phys_addr, len);
> +	dev_dbg(&vdev->dev, "%s: cache kaddr 0x%px phys_addr 0x%llx len %llx\n",
> +		__func__, fs->window_kaddr, phys_addr, cache_len);
>  
>  	fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops);
>  	if (!fs->dax_dev)
> 


-- 

Thanks,

David / dhildenb