Re: [Xen-devel] [PATCH] xen/arm: p2m: Free the p2m entry after flushing the IOMMU TLBs

[Jürgen Groß <jgross@xxxxxxxx>]

On 02.10.19 04:07, Stefano Stabellini wrote:
> + Juergen
>
> On Mon, 12 Aug 2019, Julien Grall wrote:
> > When freeing a p2m entry, all the sub-tree behind it will also be freed.
> > This may include intermediate page-tables or any l3 entry requiring to
> > drop a reference (e.g for foreign pages). As soon as pages are freed,
> > they may be re-used by Xen or another domain. Therefore it is necessary
> > to flush *all* the TLBs beforehand.
> >
> > While CPU TLBs will be flushed before freeing the pages, this is not
> > the case for IOMMU TLBs. This can be solved by moving the IOMMU TLBs
> > flush earlier in the code.
> >
> > This wasn't considered as a security issue as device passthrough on Arm
> > is not security supported.
> >
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Release-acked-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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