From 9b767139ef82279e00d86f7f1e1e8bf73d795651 Mon Sep 17 00:00:00 2001
From: madaidan <50278627+madaidan@users.noreply.github.com>
Date: Fri, 14 Feb 2020 18:52:01 +0000
Subject: [PATCH] Avoid holes in IOMMU

---
 etc/default/grub.d/40_enable_iommu.cfg | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/etc/default/grub.d/40_enable_iommu.cfg b/etc/default/grub.d/40_enable_iommu.cfg
index 1d6dd0a..6e49d49 100644
--- a/etc/default/grub.d/40_enable_iommu.cfg
+++ b/etc/default/grub.d/40_enable_iommu.cfg
@@ -3,3 +3,10 @@
 
 ## Enables IOMMU to prevent DMA attacks.
 GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX intel_iommu=on amd_iommu=on"
+
+## Disable the busmaster bit on all PCI bridges during very
+## early boot to avoid holes in IOMMU.
+##
+## https://mjg59.dreamwidth.org/54433.html
+## https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4444f8541dad16fefd9b8807ad1451e806ef1d94
+GRUB_CMDLINE_LINUX="$GRUB_CMDLINE_LINUX efi=disable_early_pci_dma"