From d0be55fbeb6ac694d15af5d1aad19cdec8cd64e5 Mon Sep 17 00:00:00 2001
From: Robin Murphy <robin.murphy@arm.com>
Date: Mon, 25 Apr 2022 13:42:03 +0100
Subject: [PATCH] iommu: Add capability for pre-boot DMA protection
Git-commit: d0be55fbeb6ac694d15af5d1aad19cdec8cd64e5
References: jsc#PED-1211
Patch-mainline: v5.19-rc1
VT-d's dmar_platform_optin() actually represents a combination of
properties fairly well standardised by Microsoft as "Pre-boot DMA
Protection" and "Kernel DMA Protection"[1]. As such, we can provide
interested consumers with an abstracted capability rather than
driver-specific interfaces that won't scale. We name it for the former
aspect since that's what external callers are most likely to be
interested in; the latter is for the IOMMU layer to handle itself.
[1] https://docs.microsoft.com/en-us/windows-hardware/design/device-experiences/oem-kernel-dma-protection
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/d6218dff2702472da80db6aec2c9589010684551.1650878781.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
drivers/iommu/intel/iommu.c | 2 ++
include/linux/iommu.h | 2 ++
2 files changed, 4 insertions(+)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index df5c62ecf942..0edf6084dc14 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4551,6 +4551,8 @@ static bool intel_iommu_capable(enum iommu_cap cap)
return domain_update_iommu_snooping(NULL);
if (cap == IOMMU_CAP_INTR_REMAP)
return irq_remapping_enabled == 1;
+ if (cap == IOMMU_CAP_PRE_BOOT_PROTECTION)
+ return dmar_platform_optin();
return false;
}
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e26cf84e5d82..4123693ae319 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -107,6 +107,8 @@ enum iommu_cap {
transactions */
IOMMU_CAP_INTR_REMAP, /* IOMMU supports interrupt isolation */
IOMMU_CAP_NOEXEC, /* IOMMU_NOEXEC flag */
+ IOMMU_CAP_PRE_BOOT_PROTECTION, /* Firmware says it used the IOMMU for
+ DMA protection and we should too */
};
/* These are the possible reserved region types */
--
2.35.3