x86/tboot: Don't disable swiotlb when iommu is forced on

After commit 327d5b2fee91c ("iommu/vt-d: Allow 32bit devices to uses DMA
domain"), swiotlb 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: 327d5b2fee91 ("iommu/vt-d: Allow 32bit devices to uses DMA domain")
Reported-and-tested-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20201125014124.4070776-1-baolu.lu@linux.intel.com
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=210237
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/x86/kernel/tboot.c b/arch/x86/kernel/tboot.c
index 420be87..ae64f98 100644 (file)
--- 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;