Re: [Xen-devel] [PATCH for-4.12] arm/p2m: do not invalidate p2m root if it is shared with IOMMU

[Julien Grall <julien.grall@xxxxxxx>]

On 29/01/2019 13:36, Andrii Anisov wrote:
> Hello Julien,
Hi,

> On 28.01.19 18:54, Julien Grall wrote:
> > There should be no Set/Way in Linux 4.14. So I am a bit confused how can 
> > even reach this code.
> Well, that is a proprietary kernel driver doing cache maintenance using Set/Way 
> operations. And I'm not sure if we can avoid that :(
Which proprietary kernel driver? And in which context are Set/Way operations 
used?

Using Set/Way is fundamentally broken partly because it does not deal with 
system caches. It also only applies to a given cache and the behavior will not 
be replicated to other CPUs. For more details, have a look at [1].
If you wonder, this worked by pure chance in older release. Running such 
software is a call for nasty behavior in your guest.
Cheers,

[1] https://www.youtube.com/watch?v=s07f82iiI-E

--
Julien Grall

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