Linux Virtualization - Jan 2011 - [PATCH] virtio-pci: add softlinks between virtio and pci

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.

Supply softlinks between these to make it possible.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

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 @@
 #include <linux/virtio_pci.h>
 #include <linux/highmem.h>
 #include <linux/spinlock.h>
+#include <linux/sysfs.h>
 
 MODULE_AUTHOR("Anthony Liguori <aliguori at us.ibm.com>");
 MODULE_DESCRIPTION("virtio-pci");
@@ -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->vdev.dev.kobj,
+				"virtio_device");
+	if (err)
+		goto out_register_device;
+
+	err = sysfs_create_link(&vp_dev->vdev.dev.kobj,
&pci_dev->dev.kobj,
+				"bus_device");
+	if (err)
+		goto out_create_link;
 
+	return 0;
+out_create_link:
+	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
+out_register_device:
+	unregister_virtio_device(&vp_dev->vdev);
 out_set_drvdata:
 	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->vdev.dev.kobj, "bus_device");
+	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
 	unregister_virtio_device(&vp_dev->vdev);
 }
 
-- 
1.7.3.2.91.g446ac

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.

Regards,

Anthony Liguori
> Supply softlinks between these to make it possible.
>
> Signed-off-by: Michael S. Tsirkin<mst at redhat.com>
> ---
>
> 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 @@
>   #include<linux/virtio_pci.h>
>   #include<linux/highmem.h>
>   #include<linux/spinlock.h>
> +#include<linux/sysfs.h>
>
>   MODULE_AUTHOR("Anthony Liguori<aliguori at us.ibm.com>");
>   MODULE_DESCRIPTION("virtio-pci");
> @@ -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->vdev.dev.kobj,
> +				"virtio_device");
> +	if (err)
> +		goto out_register_device;
> +
> +	err =
sysfs_create_link(&vp_dev->vdev.dev.kobj,&pci_dev->dev.kobj,
> +				"bus_device");
> +	if (err)
> +		goto out_create_link;
>
> +	return 0;
> +out_create_link:
> +	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
> +out_register_device:
> +	unregister_virtio_device(&vp_dev->vdev);
>   out_set_drvdata:
>   	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->vdev.dev.kobj, "bus_device");
> +	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
>   	unregister_virtio_device(&vp_dev->vdev);
>   }
>
>

On Wed, Jan 05, 2011 at 09:17:11PM +0200, 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.
> 
> Supply softlinks between these to make it possible.
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
> 
> Gleb, could you please ack that this patch below
> will be enough to fix the installer issue that
> you see?
> 
ACK. With this patch given PCI address from EDD I can find device node
by looking at /sys/devices/pci0000:00/0000:edd_bdf/virtio_device/block/
>  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 @@
>  #include <linux/virtio_pci.h>
>  #include <linux/highmem.h>
>  #include <linux/spinlock.h>
> +#include <linux/sysfs.h>
>  
>  MODULE_AUTHOR("Anthony Liguori <aliguori at us.ibm.com>");
>  MODULE_DESCRIPTION("virtio-pci");
> @@ -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->vdev.dev.kobj,
> +				"virtio_device");
> +	if (err)
> +		goto out_register_device;
> +
> +	err = sysfs_create_link(&vp_dev->vdev.dev.kobj,
&pci_dev->dev.kobj,
> +				"bus_device");
> +	if (err)
> +		goto out_create_link;
>  
> +	return 0;
> +out_create_link:
> +	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
> +out_register_device:
> +	unregister_virtio_device(&vp_dev->vdev);
>  out_set_drvdata:
>  	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->vdev.dev.kobj, "bus_device");
> +	sysfs_remove_link(&pci_dev->dev.kobj, "virtio_device");
>  	unregister_virtio_device(&vp_dev->vdev);
>  }
>  
> -- 
> 1.7.3.2.91.g446ac
--
			Gleb.

On: Wed, 05 Jan 2011 at about 19:17:11 -0000, 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.
> 
> Supply softlinks between these to make it possible.
> 
> Gleb, could you please ack that this patch below
> will be enough to fix the installer issue that
> you see?
> 
why not remove this device anchor and put the devices
under the pci device?   Proposed patch follows as a
reply.

milton