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



On 01/22/2010 04:16 AM, Daniel Veillard wrote:
> 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,

Thanks, pushed.

-- 
Chris Lalancette


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