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

Dr. David Alan Gilbert
2018-12-13T09:13:20Z

* David Hildenbrand (david@redhat.com) wrote:
> 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@redhat.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.

That makes it a very odd looking PCI device; I can see that with
virtio-pmem it makes some sense, given that it's job is to expose
arbitrary chunks of memory.

Dave

> > - 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
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK