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List: qubes-devel
Subject: [qubes-devel] Re: [Xen-devel] pre Sandy bridge IOMMU support (gm45)
From: Andrew Cooper <andrew.cooper3 () citrix ! com>
Date: 2016-01-25 10:01:37
Message-ID: 56A5F281.1080006 () citrix ! com
[Download RAW message or body]
On 24/01/16 18:21, Thierry Laurion wrote:
> Hi devs!
>
> XEN devs:
> As per short discussion with ktemkin earlier in January in #xen:
>
> "ktemkin Jan 10, 2016 16:21:50
> This test patch did appear to make the system work, though:
> https://gist.github.com/ktemkin/0e81b93654ae800a5609
>
> ktemkin Jan 10, 2016 16:24:55
> Only real difference I see between that and the upstream behavior
> (besides limiting things to dom0 so things weren't accidentally passed
> through) is the call to disable_pmr on line 117 before aborting."
>
>
>
> Makes total sense to my early understanding, since it seems that it is
> said that vt-d engine gets disabled, but disable_pmr(iommu) function
> is not called to enforce.
>
> What do you think?
There is some confusion here.
"Unfortunately, quirks specific to the Clarkdale/Nehalem integrated
graphics device (IGD) do not function correctly with Xen's VT-d
implementation"
Either
1) There is a chipset errata which prevents it from functioning
correctly, or
2) Xen's VT-d code doesn't program the chip correctly.
Which is it?
If it is 1), then there is a very good case for quirking the affected
chipsets and unilaterally disabling them. If it is 2), then the VT-d
code should be corrected.
~Andrew
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<div class="moz-cite-prefix">On 24/01/16 18:21, Thierry Laurion
wrote:<br>
</div>
<blockquote
cite="mid:CAAzJznzd67WAk=GQQDCZWETxQO1BGS+-AWHuKpWkNVJCbCqpbw@mail.gmail.com"
type="cite">
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<div>
<div>
<div>Hi devs!<br>
<br>
</div>
XEN devs:<br>
As per short discussion with ktemkin earlier in January in
#xen:<br>
<br>
"ktemkin Jan 10, 2016 16:21:50<br>
This test patch did appear to make the system work,
though: <a moz-do-not-send="true" rel="nofollow"
target="_blank"
href="https://gist.github.com/ktemkin/0e81b93654ae800a5609">https://gist.github.com/ktemkin/0e81b93654ae800a5609</a><br>
<br>
ktemkin Jan 10, 2016 16:24:55<br>
Only real difference I see between that and the upstream
behavior (besides limiting things to dom0 so things
weren't accidentally passed through) is the call to
disable_pmr on line 117 before aborting."<br>
<br>
<br>
<br>
</div>
Makes total sense to my early understanding, since it seems
that it is said that vt-d engine gets disabled, but
disable_pmr(iommu) function is not called to enforce.<br>
<br>
</div>
What do you think?<br>
</div>
</div>
</blockquote>
<br>
There is some confusion here.<br>
<br>
"Unfortunately, quirks specific to the Clarkdale/Nehalem integrated
graphics device (IGD) do not function correctly with Xen's VT-d
implementation"<br>
<br>
Either<br>
1) There is a chipset errata which prevents it from functioning
correctly, or<br>
2) Xen's VT-d code doesn't program the chip correctly.<br>
<br>
Which is it?<br>
<br>
If it is 1), then there is a very good case for quirking the
affected chipsets and unilaterally disabling them. If it is 2),
then the VT-d code should be corrected.<br>
<br>
~Andrew<br>
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