linux-kernel - Re: [PATCH v1 1/1] iommu/vt-d: Enable PRI only if the device enables PASID.

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Message-ID: <20190207212254.GA1647@otc-nc-03>
Date:   Thu, 7 Feb 2019 13:22:54 -0800
From:   "Raj, Ashok" <ashok.raj@...el.com>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, joro@...tes.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH v1 1/1] iommu/vt-d: Enable PRI only if the device enables
 PASID.

On Thu, Feb 07, 2019 at 09:15:24PM +0000, David Woodhouse wrote:
> On Thu, 2019-02-07 at 13:09 -0800, Raj, Ashok wrote:
> > You are right.. they are completely orthogonal. We just don't have
> > a way to handle the page-requests for request without PASID's.
> > 
> > There are some of the vIOMMU work to pass the PRI to who owns
> > the device, and we can certainly relax it then. This is just to reflect
> > what support exists today. FWIW, even the native driver maybe be able
> > to resolve this if supported.
> 
> As things stand, if a device makes a PRI request without a PASID, it'll
> get told that we didn't manage to bring the page in for it. Which is
> true.

That's true...it does seem to be covered already.. I can't remember
why I thought this was required :-(.. 

We can drop this patch.
> 
> What's the actual problem being fixed by this patch? Yes, we're going
> to want to hook up a way to pass the PRI to the right place... but why
> add *another* thing that's just going to have to be fixed, by reverting
> this patch?
>