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

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Date:   Thu, 07 Feb 2019 21:15:24 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     "Raj, Ashok" <ashok.raj@...el.com>
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>
Subject: Re: [PATCH v1 1/1] iommu/vt-d: Enable PRI only if the device
 enables PASID.

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.

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?


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