Re: [PATCH] xen: arm: Enable 1:1 workaround by default

[Julien Grall <julien.grall@linaro.org>]

On 11/27/2013 01:26 PM, Ian Campbell wrote:
> On Wed, 2013-11-27 at 13:23 +0000, Julien Grall wrote:
>>
>> On 11/27/2013 12:19 PM, Ian Campbell wrote:
>>> I was just about to send out patches adding the 1:1 workaround to vexpress (the
>>> foundation model is a vexpress platfrom with DMA) and sunxi.
>>>
>>> That would have meant that all platforms now implement the quirk. Instead lets
>>> just make it the default and remove the quirk.
>>>
>>> In the future this will likely be set based on the presence absence of an
>>> IOMMU, perhaps with additional overrides by the platform.
>>>
>>> A command line option no-dom0_11_mapping is provided.
>>>
>>
>> I plan to use the variable in other place, for instance in
>> common/memory.c to solve issue between ballooning and 1:1 workaround.
>>
>> It would be great if we have a function (platform_has_iommu) that we can
>> use everywhere. What do you think?
>
> I think in reality once iommu's arrive it will be a bit more subtle than
> their presence or absence, e.g. something (perhaps the platform code)
> will need to decide if all the write devices are behind an iommu such
> that the 11 can be disabled.
>
> I can unstatic opt_dom0_11_mapping and stick it in a header though. Or
> provide an accessor method.

An accessor method sounds better.

-- 
Julien Grall