Re: [PATCH] pci-assign: Hide ioport regions on lacking sysfs support

[Avi Kivity <avi@redhat.com>]

On 05/30/2012 11:47 AM, Jan Kiszka wrote:
> On 2012-05-30 10:21, Avi Kivity wrote:
>> On 05/29/2012 08:28 PM, Alex Williamson wrote:
>>> On Tue, 2012-05-29 at 20:13 +0300, Avi Kivity wrote:
>>>> On 05/29/2012 08:04 PM, Jan Kiszka wrote:
>>>>> As suggested by Alex: Instead of failing if the kernel does not allow us
>>>>> to speak to an ioport region, warn the user but, hide the region and
>>>>> continue.
>>>>
>>>>
>>>> Should we not, in addition, abort if the region is actually used?  A
>>>> guest malfunction is likely if we don't.
>>>
>>> The only way we could know that it's used is if it's the device ends up
>>> with no valid regions as a result of this.  Otherwise it's dependent on
>>> both the device and the driver whether it can still function without the
>>> i/o port regions.  Thanks,
>> 
>> If the I/O callback is called, we know it's used.
> 
> We neither expose the region to the guest (so the guest has no clue
> where to write to unless it assumes a fixed address - of which we have
> no clue) nor register any callback for it.

Ah, I thought you expose the BAR but don't back it with anything.  No
idea which approach is better, so we might as well try yours first.

-- 
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