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Re: [libvirt] [PATCH] Fix device assignment with root devices



On Thu, Jan 21, 2010 at 11:33:21AM -0500, Chris Lalancette wrote:
> The patches to add ACS checking to PCI device passthrough
> introduced a bug.  With the current code, if you try to
> passthrough a device on the root bus (i.e. bus 0), then
> it denies the passthrough.  This is because the code in
> pciDeviceIsBehindSwitchLackingACS() to check for a parent
> device doesn't take into account the possibility of the
> root bus.  If we are on the root bus, it means we
> legitimately can't find a parent, and it also means that
> we don't have to worry about whether ACS is enabled.
> Therefore return 0 (indicating we don't lack ACS) from
> pciDeviceIsBehindSwitchLackingACS().
> 
> Signed-off-by: Chris Lalancette <clalance redhat com>
> ---
>  src/util/pci.c |   19 ++++++++++++++-----
>  1 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/src/util/pci.c b/src/util/pci.c
> index 086b751..0defbfe 100644
> --- a/src/util/pci.c
> +++ b/src/util/pci.c
> @@ -1198,11 +1198,20 @@ pciDeviceIsBehindSwitchLackingACS(virConnectPtr conn,
>  {
>      pciDevice *parent;
>  
> -    if (!(parent = pciGetParentDevice(conn, dev))) {
> -        pciReportError(conn, VIR_ERR_NO_SUPPORT,
> -                       _("Failed to find parent device for %s"),
> -                       dev->name);
> -        return -1;
> +    parent = pciGetParentDevice(conn, dev);
> +    if (!parent) {
> +        /* if we have no parent, and this is the root bus, ACS doesn't come
> +         * into play since devices on the root bus can't P2P without going
> +         * through the root IOMMU.
> +         */
> +        if (dev->bus == 0)
> +            return 0;
> +        else {
> +            pciReportError(conn, VIR_ERR_NO_SUPPORT,
> +                           _("Failed to find parent device for %s"),
> +                           dev->name);
> +            return -1;
> +        }
>      }
>  
>      /* XXX we should rather fail when we can't find device's parent and

  ACK,

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
daniel veillard com  | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library  http://libvirt.org/


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