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

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.


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