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revert Ubuntu patch disabling IOMMU functionality for Skylake iGPU

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This change breaks passthrough of the iGPU on older Intel Plattforms
(Skylake)
https://forum.proxmox.com/threads/.157266

The patch was orignally applied by Ubuntu upstream for an issue
unrelated to passthrough - flickering of the display with these chips,
where some comments suggest that setting intel_iommu=igfx_off does not
fix the issue, while the patch explicitly says it does the same as
setting intel_iommu=igfx_off - my quick glance at the code agrees with
the patch author, with the downside that with the patch you cannot
enable it again via kernel_cmdline.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2062951

As this is a regression, and our user-base does not seem to have
encountered the issue with flickering displays simply revert the
change for now. A proper fix seems to be in the makings in linux
upstream (according to the launchpad issue)

I tested this on an old machine we had lying around - reverting the
patch suppressed the message:
pci 0000:00:02.0: DMAR: Disabling IOMMU for graphics on this chipset
(also did not notice any flickering in a short graphic session
(wayland+kde)).

I'd suggest pulling this also into our 6.8 kernel (but this can also happen
after we get some feedback that it indeed fixes the issue of the
reporters in the forum)

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
This commit is contained in:
Stoiko Ivanov 2024-11-26 17:36:36 +01:00 committed by Thomas Lamprecht
parent 21160ccd40
commit d4dcf2b536
1 changed files with 53 additions and 0 deletions
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53
patches/kernel/0017-Revert-UBUNTU-SAUCE-iommu-intel-disable-DMAR-for-SKL.patch Normal file
View File

@ -0,0 +1,53 @@
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Stoiko Ivanov <s.ivanov@proxmox.com>
Date: Mon, 25 Nov 2024 11:10:35 +0100
Subject: [PATCH] Revert "UBUNTU: SAUCE: iommu/intel: disable DMAR for SKL
integrated gfx"
Some of our users use the iGPU for PCI-passthrough on those
plattforms, which seems broken with this commit added.
https://forum.proxmox.com/threads/.157266
This reverts commit b310f5f58c83756fc164f7d391d76f0df9cc65c3.
---
drivers/iommu/intel/iommu.c | 27 ---------------------------
1 file changed, 27 deletions(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 34c8b02ca7878..a27cbc22148fa 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4766,33 +4766,6 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1632, quirk_iommu_igfx);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163A, quirk_iommu_igfx);
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x163D, quirk_iommu_igfx);
-/* SKL */
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1906, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1913, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x190E, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1915, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1902, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x190A, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x190B, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1917, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1916, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1921, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x191E, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1912, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x191A, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x191B, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x191D, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1923, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1926, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1927, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x192A, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x192B, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x192D, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x1932, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x193A, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x193B, quirk_iommu_igfx);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x193D, quirk_iommu_igfx);
-
/* disable IPU dmar support */
DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, PCI_ANY_ID, quirk_iommu_ipu);