Re: pre Sandy bridge IOMMU support (gm45)

[Thierry Laurion <thierry.laurion@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 2282 bytes --]

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?

QUBES devs:
I'm still trying to understand how to apply this patch to qubes_builder to
actually build a test iso or xen.gz image and report. All Qubes patches
seem to be applied from git to local directory structure. Looking inside
the code to understand how to generate the provided patch to git can apply
it to local chrooted environment when building. Any documentation you could
point me to would be greatly appreciated, as any feedback to actually fix
the issue stopping this laptop from being a nearly perfect candidate for
Qubes.


Thierry

Le sam. 23 janv. 2016 à 02:37, Thierry Laurion <thierry.laurion@gmail.com>
a écrit :

> Hey devs,
>
> Thinkpad x200 p8600 laptops have vt-d, vt-x and tpm. They also have intel
> integrated graphics 4 Series (gm45 chipset), supported through i915 driver.
>
> In December, a fix got introduced to Xen 4.6 through iommu=no-igfx switch.
> Before that fix, it was impossible to boot xen without passing iommu=0.
>
> With iommu=no-igfx passed on, Qubes boots xen, kernel, dom0 and domu until
> some graphic rendering is done from a domu to dom0 xserver.
>
> I'm trying to push forward IOMMU support of gm45 chipset here. The problem
> is between i915 and xen iommu support for sure, but there is no crash or
> interesting debugging information given on a serial console.
>
> Any dev help is welcome since that beast and t400 would be excellent Qubes
> candidates once that problem is fixed. I posted in December on the list
> just before Christmas but I guess the timing wasn't right;)
>
> Thanks for your help.
> Thierry
>

[-- Attachment #1.2: Type: text/html, Size: 2767 bytes --]

[-- Attachment #2: xen.diff --]
[-- Type: text/x-patch, Size: 398 bytes --]

--- ./drivers/passthrough/vtd/iommu.c.bak	2016-01-24 12:55:15.020267553 -0500
+++ ./drivers/passthrough/vtd/iommu.c	2016-01-24 12:57:14.754138262 -0500
@@ -717,6 +717,7 @@
         {
             dprintk(XENLOG_WARNING VTDPREFIX,
                     "BIOS did not enable IGD for VT properly.  Disabling IGD VT-d engine.\n");
+            disable_pmr(iommu);
             return;
         }
     }

[-- Attachment #3: Type: text/plain, Size: 126 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel