Xen devel - Nov 2009 - [PATCH] Fix casting usage in xen_create_msi_irq.

rc is int, domid is unsigned int. The casting of negatives values
to domid results in wrap where -16 becomes 0xfff0. If we check
for rc (instead of domid) and find a negative value (which you can''t
with domid) then we will default to DOMID_SELF - which is exactly
what this line was intending to do earlier but failed to do.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/xen/events.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index adc8c09..67598bc 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -678,7 +678,7 @@ int xen_create_msi_irq(struct pci_dev *dev, struct msi_desc
*msidesc,
 	/* Walk the XenStore keys to see if the device is assigned to any
 	 * domain. If so, extract the domain id. */
 	domid = rc = xenbus_walk( "/local/domain/0", get_domid_for_dev,
dev);
-	if (domid <= 0)
+	if (rc <= 0)
 		domid = DOMID_SELF;
 
 	memset(&map_irq, 0, sizeof(map_irq));
-- 
1.6.2.5


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Jeremy, 

Seems this fix is still not in xen/master branch, pv-ops dom0 is blocked to
enable SR-IOV devices without it. Could you merge it into xen/master branch ?

Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>

Xiantao


Konrad Rzeszutek Wilk wrote:
> rc is int, domid is unsigned int. The casting of negatives values
> to domid results in wrap where -16 becomes 0xfff0. If we check
> for rc (instead of domid) and find a negative value (which you
can''t
> with domid) then we will default to DOMID_SELF - which is exactly
> what this line was intending to do earlier but failed to do.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  drivers/xen/events.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index adc8c09..67598bc 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -678,7 +678,7 @@ int xen_create_msi_irq(struct pci_dev *dev,
>  	struct msi_desc *msidesc, /* Walk the XenStore keys to see if the
>  	 device is assigned to any * domain. If so, extract the domain id.
>  	*/ domid = rc = xenbus_walk( "/local/domain/0",
get_domid_for_dev,
> dev); -	if (domid <= 0)
> +	if (rc <= 0)
>  		domid = DOMID_SELF;
> 
>  	memset(&map_irq, 0, sizeof(map_irq));

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