* [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx
@ 2016-12-05 21:58 Kees Cook
2016-12-05 22:07 ` David Woodhouse
0 siblings, 1 reply; 5+ messages in thread
From: Kees Cook @ 2016-12-05 21:58 UTC (permalink / raw)
To: Daniel Vetter
Cc: iommu, Jani Nikula, intel-gfx, David Woodhouse, Joerg Roedel,
linux-kernel
This blacklists the Q35 integrated graphics so IOMMU can be otherwise
enabled. Without this, a Q35 system can only enable IOMMU when booting
with "intel_iommu=on,igfx_off" but not "intel_iommu=on".
00:02.0 0300: 8086:29b2 (rev 02) (prog-if 00 [VGA controller])
Subsystem: 8086:4f4a
Flags: bus master, fast devsel, latency 0, IRQ 32
Memory at e0380000 (32-bit, non-prefetchable) [size=512K]
I/O ports at 2460 [size=8]
Memory at d0000000 (32-bit, prefetchable) [size=256M]
Memory at e0200000 (32-bit, non-prefetchable) [size=1M]
Expansion ROM at <unassigned> [disabled]
Capabilities: <access denied>
Kernel driver in use: i915
Kernel modules: i915
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/iommu/intel-iommu.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d8376c2d18b3..24e5b06834ae 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -5327,6 +5327,7 @@ static void quirk_iommu_g4x_gfx(struct pci_dev *dev)
dmar_map_gfx = 0;
}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x29b2, quirk_iommu_g4x_gfx);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2a40, quirk_iommu_g4x_gfx);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2e00, quirk_iommu_g4x_gfx);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2e10, quirk_iommu_g4x_gfx);
--
2.7.4
--
Kees Cook
Nexus Security
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx
2016-12-05 21:58 [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx Kees Cook
@ 2016-12-05 22:07 ` David Woodhouse
2016-12-05 22:18 ` Kees Cook
0 siblings, 1 reply; 5+ messages in thread
From: David Woodhouse @ 2016-12-05 22:07 UTC (permalink / raw)
To: Kees Cook, Daniel Vetter
Cc: iommu, Jani Nikula, intel-gfx, Joerg Roedel, linux-kernel
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On Mon, 2016-12-05 at 13:58 -0800, Kees Cook wrote:
> This blacklists the Q35 integrated graphics so IOMMU can be otherwise
> enabled. Without this, a Q35 system can only enable IOMMU when booting
> with "intel_iommu=on,igfx_off" but not "intel_iommu=on".
Hm, is this definitely the same bug? Or is it something different, and
perhaps a BIOS issue? There are many of those...
--
dwmw2
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx
2016-12-05 22:07 ` David Woodhouse
@ 2016-12-05 22:18 ` Kees Cook
2016-12-05 22:47 ` David Woodhouse
0 siblings, 1 reply; 5+ messages in thread
From: Kees Cook @ 2016-12-05 22:18 UTC (permalink / raw)
To: David Woodhouse
Cc: Daniel Vetter, iommu, Jani Nikula, intel-gfx, Joerg Roedel, LKML
On Mon, Dec 5, 2016 at 2:07 PM, David Woodhouse <dwmw2@infradead.org> wrote:
> On Mon, 2016-12-05 at 13:58 -0800, Kees Cook wrote:
>> This blacklists the Q35 integrated graphics so IOMMU can be otherwise
>> enabled. Without this, a Q35 system can only enable IOMMU when booting
>> with "intel_iommu=on,igfx_off" but not "intel_iommu=on".
>
> Hm, is this definitely the same bug? Or is it something different, and
> perhaps a BIOS issue? There are many of those...
Hm, I have no idea. :) What would I look for in the BIOS?
I figured since g4 was busted, surely q35 was too, since it's even older...
-Kees
--
Kees Cook
Nexus Security
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx
2016-12-05 22:18 ` Kees Cook
@ 2016-12-05 22:47 ` David Woodhouse
2016-12-05 23:16 ` Kees Cook
0 siblings, 1 reply; 5+ messages in thread
From: David Woodhouse @ 2016-12-05 22:47 UTC (permalink / raw)
To: Kees Cook
Cc: Daniel Vetter, iommu, Jani Nikula, intel-gfx, Joerg Roedel, LKML
On Mon, 2016-12-05 at 14:18 -0800, Kees Cook wrote:
> Hm, I have no idea. :) What would I look for in the BIOS?
For a start, what is the actual failure mode?
> I figured since g4 was busted, surely q35 was too, since it's even
> older...
Oh no, they all have different failures. Intel never actually *tested*
their graphics hardware before shipping it, but IIRC it was only Q4x
where we concluded the hardware was just too broken to live.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx
2016-12-05 22:47 ` David Woodhouse
@ 2016-12-05 23:16 ` Kees Cook
0 siblings, 0 replies; 5+ messages in thread
From: Kees Cook @ 2016-12-05 23:16 UTC (permalink / raw)
To: David Woodhouse
Cc: Daniel Vetter, iommu, Jani Nikula, intel-gfx, Joerg Roedel, LKML
On Mon, Dec 5, 2016 at 2:47 PM, David Woodhouse <dwmw2@infradead.org> wrote:
> On Mon, 2016-12-05 at 14:18 -0800, Kees Cook wrote:
>> Hm, I have no idea. :) What would I look for in the BIOS?
>
> For a start, what is the actual failure mode?
Based on initial testing (not that I've spent tons of time with it,
since I need that machine running): at graphics init, entire system
hangs. :P
>> I figured since g4 was busted, surely q35 was too, since it's even
>> older...
>
> Oh no, they all have different failures. Intel never actually *tested*
> their graphics hardware before shipping it, but IIRC it was only Q4x
> where we concluded the hardware was just too broken to live.
Wheee!
-Kees
--
Kees Cook
Nexus Security
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2016-12-05 23:17 UTC | newest]
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2016-12-05 21:58 [PATCH] iommu/intel: disable DMAR for Q35 integrated gfx Kees Cook
2016-12-05 22:07 ` David Woodhouse
2016-12-05 22:18 ` Kees Cook
2016-12-05 22:47 ` David Woodhouse
2016-12-05 23:16 ` Kees Cook
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