Re: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table per PCI segment

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.09.2019 11:20, Paul Durrant wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 24 September 2019 10:10
>> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
>> Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Andrew Cooper 
>> <Andrew.Cooper3@xxxxxxxxxx>
>> Subject: Re: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table 
>> per PCI segment
>>
>> On 23.09.2019 18:30, Paul Durrant wrote:
>>>> -----Original Message-----
>>>> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
>>>> Beulich
>>>> Sent: 19 September 2019 14:25
>>>> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
>>>> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Suravee Suthikulpanit
>> <suravee.suthikulpanit@xxxxxxx>
>>>> Subject: [Xen-devel] [PATCH v6 7/8] AMD/IOMMU: allocate one device table 
>>>> per PCI segment
>>>>
>>>> Having a single device table for all segments can't possibly be right.
>>>
>>> The copy of the spec. I have says (on page 253: Fixed-Length IVHD
>>> Blocks) that IVHD entries must have a segment group of 0, so can't
>>> the code just require iommu->seg == 0?
>>
>> The wording in my version is "At this time, only PCI Segment Group 0 is
>> supported." This suggests to me that it is not a good idea to have logic
>> baked in that depends on this remaining true. I realize though that there
>> are more places than just this one where we (have to) assume segment 0
>> (all in iommu_acpi.c, and all marked with an XXX comment).
>>
> 
> Ok. Fair enough. I just wasn't sure it was worth doing this change at the
> moment;

The thing that I found really disgusting was the global (i.e. not even
static) variable "device_table". And simply making it static would still
have left things in too ugly a state for my taste.

> but it doesn't hurt, so you can add my R-b.

Thanks.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel