Re: [PATCH] virtio-pci: add softlinks between virtio and pci

From: Anthony Liguori
Date: Wed Jan 05 2011 - 15:08:38 EST

On 01/05/2011 02:05 PM, Michael S. Tsirkin wrote:
On Wed, Jan 05, 2011 at 01:28:34PM -0600, Anthony Liguori wrote:
On 01/05/2011 01:17 PM, Michael S. Tsirkin wrote:
We sometimes need to map between the virtio device and
the given pci device. One such use is OS installer that
gets the boot pci device from BIOS and needs to
find the relevant block device. Since it can't,
installation fails.
I have no objection to this patch but I'm a tad confused by the description.

I assume you mean the installer is querying the boot device via
int13 get driver parameters such that it returns the pci address of
the device?

Or is it querying geometry information and then trying to find the
best match block device?

If it's the former, I don't really understand the need for a
backlink since the PCI address gives you a link to the block device.
OTOH, if it's the later, it would make sense but then your
description doesn't really make much sense.

At any rate, a better commit message would be helpful in explaining
the need for this.


Anthony Liguori
OK just to clarify: we get pci address from BIOS
and need the virtio device to get at the linux device
(e.g. block) in the end. Thus the link from pci to virtio.
I also added a backlink since I thought it's handy.

Does this answer the questions?

Rusty rewrites my commit logs anyway, he has better style :)

It helps. The real reason this is needed is because in a normal device, there is only one struct device whereas with virtio-pci, the virtio-pci device has a struct device and then the actual virtio device has another one. There's probably a better way to handle this in sysfs making virtio-pci a proper bus with only a single device as a child or something like that.

But the links are probably an easier solution.


Anthony Liguori

Supply softlinks between these to make it possible.

Signed-off-by: Michael S. Tsirkin<mst@xxxxxxxxxx>

Gleb, could you please ack that this patch below
will be enough to fix the installer issue that
you see?

drivers/virtio/virtio_pci.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)

diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
index ef8d9d5..06eb2f8 100644
--- a/drivers/virtio/virtio_pci.c
+++ b/drivers/virtio/virtio_pci.c
@@ -25,6 +25,7 @@

MODULE_AUTHOR("Anthony Liguori<aliguori@xxxxxxxxxx>");
@@ -667,8 +668,21 @@ static int __devinit virtio_pci_probe(struct pci_dev *pci_dev,
if (err)
goto out_set_drvdata;

- return 0;
+ err = sysfs_create_link(&pci_dev->dev.kobj,&vp_dev->,
+ "virtio_device");
+ if (err)
+ goto out_register_device;
+ err = sysfs_create_link(&vp_dev->,&pci_dev->dev.kobj,
+ "bus_device");
+ if (err)
+ goto out_create_link;

+ return 0;
+ sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
+ unregister_virtio_device(&vp_dev->vdev);
pci_set_drvdata(pci_dev, NULL);
pci_iounmap(pci_dev, vp_dev->ioaddr);
@@ -685,6 +699,8 @@ static void __devexit virtio_pci_remove(struct pci_dev *pci_dev)
struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);

+ sysfs_remove_link(&vp_dev->, "bus_device");
+ sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");

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