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SubjectRe: [PATCH 04/20] virtio: Implement get_shm_region for PCI transport
On Tue, Mar 10, 2020 at 11:04:37AM +0000, Stefan Hajnoczi wrote:
> On Wed, Mar 04, 2020 at 11:58:29AM -0500, Vivek Goyal wrote:
> > diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> > index 7abcc50838b8..52f179411015 100644
> > --- a/drivers/virtio/virtio_pci_modern.c
> > +++ b/drivers/virtio/virtio_pci_modern.c
> > @@ -443,6 +443,111 @@ static void del_vq(struct virtio_pci_vq_info *info)
> > vring_del_virtqueue(vq);
> > }
> >
> > +static int virtio_pci_find_shm_cap(struct pci_dev *dev,
> > + u8 required_id,
> > + u8 *bar, u64 *offset, u64 *len)
> > +{
> > + int pos;
> > +
> > + for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
>
> Please fix the mixed tabs vs space indentation in this patch.

Will do. There are plenty of these in this patch.

>
> > +static bool vp_get_shm_region(struct virtio_device *vdev,
> > + struct virtio_shm_region *region, u8 id)
> > +{
> > + struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> > + struct pci_dev *pci_dev = vp_dev->pci_dev;
> > + u8 bar;
> > + u64 offset, len;
> > + phys_addr_t phys_addr;
> > + size_t bar_len;
> > + int ret;
> > +
> > + if (!virtio_pci_find_shm_cap(pci_dev, id, &bar, &offset, &len)) {
> > + return false;
> > + }
> > +
> > + ret = pci_request_region(pci_dev, bar, "virtio-pci-shm");
> > + if (ret < 0) {
> > + dev_err(&pci_dev->dev, "%s: failed to request BAR\n",
> > + __func__);
> > + return false;
> > + }
> > +
> > + phys_addr = pci_resource_start(pci_dev, bar);
> > + bar_len = pci_resource_len(pci_dev, bar);
> > +
> > + if (offset + len > bar_len) {
> > + dev_err(&pci_dev->dev,
> > + "%s: bar shorter than cap offset+len\n",
> > + __func__);
> > + return false;
> > + }
> > +
> > + region->len = len;
> > + region->addr = (u64) phys_addr + offset;
> > +
> > + return true;
> > +}
>
> Missing pci_release_region()?

Good catch. We don't have a mechanism to call pci_relese_region() and
virtio-mmio device's ->get_shm_region() implementation does not even
seem to reserve the resources.

So how about we leave this resource reservation to the caller.
->get_shm_region() just returns the addr/len pair of requested resource.

Something like this patch.
---
drivers/virtio/virtio_pci_modern.c | 8 --------
fs/fuse/virtio_fs.c | 13 ++++++++++---
2 files changed, 10 insertions(+), 11 deletions(-)
Index: redhat-linux/fs/fuse/virtio_fs.c
===================================================================
--- redhat-linux.orig/fs/fuse/virtio_fs.c 2020-03-10 09:13:34.624565666 -0400
+++ redhat-linux/fs/fuse/virtio_fs.c 2020-03-10 14:11:10.970284651 -0400
@@ -763,11 +763,18 @@ static int virtio_fs_setup_dax(struct vi
if (!have_cache) {
dev_notice(&vdev->dev, "%s: No cache capability\n", __func__);
return 0;
- } else {
- dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n",
- cache_reg.len, cache_reg.addr);
}

+ if (!devm_request_mem_region(&vdev->dev, cache_reg.addr, cache_reg.len,
+ dev_name(&vdev->dev))) {
+ dev_warn(&vdev->dev, "could not reserve region addr=0x%llx"
+ " len=0x%llx\n", cache_reg.addr, cache_reg.len);
+ return -EBUSY;
+ }
+
+ dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n", cache_reg.len,
+ cache_reg.addr);
+
pgmap = devm_kzalloc(&vdev->dev, sizeof(*pgmap), GFP_KERNEL);
if (!pgmap)
return -ENOMEM;
Index: redhat-linux/drivers/virtio/virtio_pci_modern.c
===================================================================
--- redhat-linux.orig/drivers/virtio/virtio_pci_modern.c 2020-03-10 08:51:36.886565666 -0400
+++ redhat-linux/drivers/virtio/virtio_pci_modern.c 2020-03-10 13:43:15.168753543 -0400
@@ -511,19 +511,11 @@ static bool vp_get_shm_region(struct vir
u64 offset, len;
phys_addr_t phys_addr;
size_t bar_len;
- int ret;

if (!virtio_pci_find_shm_cap(pci_dev, id, &bar, &offset, &len)) {
return false;
}

- ret = pci_request_region(pci_dev, bar, "virtio-pci-shm");
- if (ret < 0) {
- dev_err(&pci_dev->dev, "%s: failed to request BAR\n",
- __func__);
- return false;
- }
-
phys_addr = pci_resource_start(pci_dev, bar);
bar_len = pci_resource_len(pci_dev, bar);

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