[PATCH 1/1] x86/tboot: Don't disable swiotlb when iommu is forced on

Lu Baolu
2020-11-25T01:48:56Z

After commit 327d5b2fee91c ("iommu/vt-d: Allow 32bit devices to uses DMA
domain"), swiotbl could also be used for direct memory access if IOMMU
is enabled but a device is configured to pass through the DMA translation.
Keep swiotlb when IOMMU is forced on, otherwise, some devices won't work
if "iommu=pt" kernel parameter is used.

Fixes: 327d5b2fee91c ("iommu/vt-d: Allow 32bit devices to uses DMA domain")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=210237
Reported-and-tested-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
arch/x86/kernel/tboot.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 420be871d9d4..ae64f98ec2ab 100644
--- a/arch/x86/kernel/tboot.c
+++ b/arch/x86/kernel/tboot.c
@@ -514,13 +514,10 @@ int tboot_force_iommu(void)
if (!tboot_enabled())
return 0;

- if (no_iommu || swiotlb || dmar_disabled)
+ if (no_iommu || dmar_disabled)
pr_warn("Forcing Intel-IOMMU to enabled\n");

dmar_disabled = 0;
-#ifdef CONFIG_SWIOTLB
- swiotlb = 0;
-#endif
no_iommu = 0;

return 1;
--
2.25.1