Re: [Xen-devel] [PATCH] amd iommu: Dump flags of IO page faults

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.09.12 at 12:00, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:

> Friday, September 7, 2012, 11:53:36 AM, you wrote:
> 
>>>>> On 07.09.12 at 09:32, Sander Eikelenboom <linux@xxxxxxxxxxxxxx> wrote:
>>> 4.1:    Capabilities: [54] MSI: Enable- Count=1/1 Maskable- 64bit+
>>> 4.2:    Capabilities: [54] MSI: Enable+ Count=1/1 Maskable- 64bit+
> 
>> No surprise you're not seeing any faults on 4.1 - there's no way
>> they could get reported. I'm somewhat hesitant to pull the
>> workaround patch from 4.2 into 4.1, as it's wrong for the kernel
>> to touch the MSI setting of the IOMMU (which is under the
>> control of Xen) in the first place, but the kernel side patch I had
>> submitted a while ago wasn't received well. And that patch isn't
>> really small, and it would remain to be seen what other
>> dependencies it would have...
> 
> Ok so that would mean that in the 4.1 case, the IOMMU is doing nothing ?

No, it just can't report faults (they would need to be polled for).
Also, saying "in the 4.1 case" is wrong here - this really depends
on whether you have an affected Dom0 kernel. Things work fine
if the Dom0 kernel doesn't trample over Xen's setup.

Jan


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