Re: [Xen-devel] [PATCH] x86/ats: Disable Address Translation Services by default

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.08.14 at 10:18, <suravee.suthikulpanit@xxxxxxx> wrote:
> On 08/28/2014 02:32 AM, Jan Beulich wrote:
>>>>> On 28.08.14 at 09:08, <suravee.suthikulpanit@xxxxxxx> wrote:
>>> I have verified that PCI device pass-through works with ATS disabled.
>>> Although, could you please help described how "asynchronous queued
>>> invalidation support" supposed to work?
>>
>> Are asking about the abstract model, or the specific implementation?
>> The former is quite obvious is think (utilize the respective interrupt to
>> get notified of completions and suspend the execution in the current
>> context until then),
> 
> So, what Andrew is saying is that the current implementation which uses 
> the "synchronous wait for completion" is not safe? May be I'm not 
> getting the whole picture here of how it is unsafe.

It may be spinning for up to a second, and for ATS it would really
need to be spinning for up to 60 seconds (perhaps even 90,
depending on how to interpret the spec).

Jan


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