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Re: [Qemu-devel] [PATCH v2 00/13] iommu: support txattrs, support TCG ex

From: Peter Xu
Subject: Re: [Qemu-devel] [PATCH v2 00/13] iommu: support txattrs, support TCG execution, implement TZ MPC
Date: Tue, 5 Jun 2018 21:25:01 +0800
User-agent: Mutt/1.9.5 (2018-04-13)

On Tue, Jun 05, 2018 at 10:13:12AM +0100, Peter Maydell wrote:
> On 5 June 2018 at 08:39, Peter Xu <address@hidden> wrote:
> > On Mon, Jun 04, 2018 at 04:29:28PM +0100, Peter Maydell wrote:
> >> Hi; this is v2 of my iommu patchset, which does:
> >>  * support IOMMUs that are aware of memory transaction attributes and
> >>    may generate different translations for different attributes
> >>  * support TCG execution out of memory which is behind an IOMMU
> >>  * implement the Arm TrustZone Memory Protection Controller
> >>    (which needs both the above features in the IOMMU core code)
> >>  * use the MPC in the mps2-an505 board
> > It seems that this series is still using the IOMMU index way.  In case
> > I missed anything... Could you elaborate a bit on why this IOMMU index
> > solution is preferred comparing to the way to pass in MemTxAttrs?  Or
> > was there any further discussion I missed on the topic?
> >
> > My last post to previous series is here:
> >
> > https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg05702.html
> >
> > In that, I was still confused on why we couldn't use the existing
> > MemTxAttrs directly instead of the new IOMMU index (and I explained on
> > why that was prefered at least to me). I didn't see replies
> > afterwards.
> Broadly speaking I didn't think I had any further better
> explanation than I'd already given in that thread, eg here:
> https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg05250.html
> and here:
> https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg05513.html
> If you want to make a specific (detailed) counterproposal of a
> different API, I'm happy to look at whether that works for
> the use cases I care about and whether it's a nicer way to do it.

I posted a few pesudo code (ok, it can actually compile...) to show
what I meant.  Please have a look there:

  [RFC 0/3] memory: enhance IOMMU notifier to support USER bit

I very suspect I missed some important requirement there but I cannot
really figure it out myself.  Hope these patches can either provide an
alternative solution on the problem, or help me to figure out what I
missed.   Thanks,

Peter Xu

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