Re: [Xen-devel] [PATCH 1/3] x86/p2m: tighten conditions of IOMMU mapping updates

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Sep 22, 2015 at 08:15:39AM -0600, Jan Beulich wrote:
> >>> On 21.09.15 at 16:02, <JBeulich@xxxxxxxx> wrote:
> > In the EPT case permission changes should also result in updates or
> > TLB flushes.
> > 
> > In the NPT case the old MFN does not depend on the new entry being
> > valid (but solely on the old one), and the need to update or TLB-flush
> > again also depends on permission changes.
> > 
> > In the shadow mode case, iommu_hap_pt_share should be ignored.
> > 
> > Furthermore in the NPT/shadow case old intermediate page tables must
> > be freed only after IOMMU side updates/flushes have got carried out.
> > 
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Wei,
> 
> I'm sorry, I forgot to Cc you on the patch and state that I think this
> should be considered for 4.6.
> 

While I think having this issue fixed for 4.6 would be nice,  I would
like to ...

> Jan
> 
> > ---
> > In addition to the fixes here it looks to me as if both EPT and
> > NPT/shadow code lack invalidation of IOMMU side paging structure
> > caches, i.e. further changes may be needed. Am I overlooking something?

have this question answered. Having a "fix" that doesn't actually fix
the issue is not very useful...

Wei.

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