[PATCH AUTOSEL 5.5 458/542] iommu/vt-d: Mark firmware tainted if RMRR fails sanity check

[Sasha Levin]

From: Barret Rhoden <brho@xxxxxxxxxx>

[ Upstream commit f5a68bb0752e0cf77c06f53f72258e7beb41381b ]

RMRR entries describe memory regions that are DMA targets for devices
outside the kernel's control.

RMRR entries that fail the sanity check are pointing to regions of
memory that the firmware did not tell the kernel are reserved or
otherwise should not be used.

Instead of aborting DMAR processing, this commit marks the firmware
as tainted. These RMRRs will still be identity mapped, otherwise,
some devices, e.x. graphic devices, will not work during boot.

Signed-off-by: Barret Rhoden <brho@xxxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Fixes: f036c7fa0ab60 ("iommu/vt-d: Check VT-d RMRR region in BIOS is reported as reserved")
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/iommu/intel-iommu.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 541896ab3d086..dfedbb04f647d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4320,12 +4320,16 @@ int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
 {
 	struct acpi_dmar_reserved_memory *rmrr;
 	struct dmar_rmrr_unit *rmrru;
-	int ret;
 
 	rmrr = (struct acpi_dmar_reserved_memory *)header;
-	ret = arch_rmrr_sanity_check(rmrr);
-	if (ret)
-		return ret;
+	if (arch_rmrr_sanity_check(rmrr))
+		WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND,
+			   "Your BIOS is broken; bad RMRR [%#018Lx-%#018Lx]\n"
+			   "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
+			   rmrr->base_address, rmrr->end_address,
+			   dmi_get_system_info(DMI_BIOS_VENDOR),
+			   dmi_get_system_info(DMI_BIOS_VERSION),
+			   dmi_get_system_info(DMI_PRODUCT_VERSION));
 
 	rmrru = kzalloc(sizeof(*rmrru), GFP_KERNEL);
 	if (!rmrru)
-- 
2.20.1