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

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Date:   Sat, 16 Mar 2019 17:33:25 -0700
From:   Liu Bo <obuil.liubo@...il.com>
To:     Vivek Goyal <vgoyal@...hat.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, miklos@...redi.hu,
        Stefan Hajnoczi <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 Mon, Dec 10, 2018 at 9:57 AM Vivek Goyal <vgoyal@...hat.com> 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? */
> -       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,

Just in case you haven't noticed/fixed this problem, it should be

+ .end = phys_addr + cache_len - 1,

because resource_size() counts %size as "end - start + 1".
The end result of the above is a "conflicting page map" warning when
specifying a second virtio-fs pci device.

I'll send a patch for this, and feel free to take it along with the
patchset if needed.

thanks,
liubo

>         };
>
>         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)
> --
> 2.13.6
>