From 97cb534d72d8ded3cc4c123ace66fb05fff9139d Mon Sep 17 00:00:00 2001
From: Wolfgang Müller
Date: Mon, 17 May 2021 11:16:16 +0200
Subject: kernel-5.10: Add patch fixing a kernel panic with 5.10.37

We expect this to be fixed in 38, so make sure to only apply it to this
specific kernel version.
---
 .../0001-iommu-vt-d-Fix-kernel-panic-on-boot.patch | 71 ++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 kernel-5.10/patches/sys-kernel/gentoo-sources-5.10.37/0001-iommu-vt-d-Fix-kernel-panic-on-boot.patch

diff --git a/kernel-5.10/patches/sys-kernel/gentoo-sources-5.10.37/0001-iommu-vt-d-Fix-kernel-panic-on-boot.patch b/kernel-5.10/patches/sys-kernel/gentoo-sources-5.10.37/0001-iommu-vt-d-Fix-kernel-panic-on-boot.patch
new file mode 100644
index 0000000..fe1285c
--- /dev/null
+++ b/kernel-5.10/patches/sys-kernel/gentoo-sources-5.10.37/0001-iommu-vt-d-Fix-kernel-panic-on-boot.patch
@@ -0,0 +1,71 @@
+From c2f99461fbdc8412052e526a7c998408543a8d2d Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Wolfgang=20M=C3=BCller?= <wolf@oriole.systems>
+Date: Mon, 17 May 2021 10:27:49 +0200
+Subject: [PATCH] iommu/vt-d: Fix kernel panic on boot
+
+The LTS release 5.10.37 would panic immediately on boot with the
+following backtrace:
+
+Call Trace:
+ domain_mapping+0x16/0x90
+ __iommu_map+0xcd/0x120
+ iommu_create_device_direct_mappins.isra.0+0x175/0x210
+ bus_iommu_probe+0x15a/0x290
+ bus_set_iommu+0x7e/0xd0
+ intel_iommu_init+0xf84/0x112b
+ ? e820__memblock_setup+0x76/0x76
+ pci_iommu_init+0x11/0x3a
+ do_one_initcall+0x5a/0x190
+ kernel_init_freeable+0x140/0x185
+ ? rest_init+0xa4/0xa4
+ kernel_init+0x5/0xfc
+ ret_from_fork+0x22/0x30
+Modules linked in:
+CR2: 0000000000000000
+---[ end trace 0904a2a0169baf8a ]--
+RIP: 0010:__domain_mapping+0xa1/0x3a0
+
+Commit 416fa531c816 (iommu/vt-d: Preset Access/Dirty bits for IOVA over
+FL, 2021-01-15) seemed to have introduced this problem by changing the
+conditional:
+
+if (!sg) { ...
+        sg_res = nr_pages;
+        pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
+}
+
+to an unconditional:
+
+pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
+
+Whilst we do not know exactly what went wrong, this patch was proposed
+in [1] and then reworked into fixing the original commit in [2].
+
+See also [3] for our initial report.
+
+[1] https://bugzilla.kernel.org/show_bug.cgi?id=213077#c7
+[2] https://lore.kernel.org/lkml/20210517034913.3432-1-baolu.lu@linux.intel.com/
+[3] https://lore.kernel.org/lkml/20210515132855.4bn7ve2ozvdhpnj4@nabokov.fritz.box/
+---
+ drivers/iommu/intel/iommu.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
+index db9bf5ac0722..eececdeaa40f 100644
+--- a/drivers/iommu/intel/iommu.c
++++ b/drivers/iommu/intel/iommu.c
+@@ -2373,7 +2373,10 @@ static int __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
+ 		}
+ 	}
+ 
+-	pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
++	if (!sg) {
++		sg_res = nr_pages;
++		pteval = ((phys_addr_t)phys_pfn << VTD_PAGE_SHIFT) | attr;
++	}
+ 
+ 	while (nr_pages > 0) {
+ 		uint64_t tmp;
+-- 
+2.31.1
+
-- 
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