[PATCH v3 01/15] iommu: Add IOMMU_CAP_ENFORCE_CACHE_COHERENCY

[Jason Gunthorpe <jgg@nvidia.com>]

This queries if a domain linked to a device should expect to support
enforce_cache_coherency() so iommufd can negotiate the rules for when a
domain should be shared or not.

For iommufd a device that declares IOMMU_CAP_ENFORCE_CACHE_COHERENCY will
not be attached to a domain that does not support it.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/amd/iommu.c   | 2 ++
 drivers/iommu/intel/iommu.c | 4 ++++
 include/linux/iommu.h       | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index d3b39d0416fa32..d0802cab2a2f0c 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2286,6 +2286,8 @@ static bool amd_iommu_capable(struct device *dev, enum iommu_cap cap)
 		return false;
 	case IOMMU_CAP_PRE_BOOT_PROTECTION:
 		return amdr_ivrs_remap_support;
+	case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:
+		return true;
 	default:
 		break;
 	}
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 48cdcd0a5cf346..438ba997fa230e 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4458,7 +4458,11 @@ static bool intel_iommu_capable(struct device *dev, enum iommu_cap cap)
 		return irq_remapping_enabled == 1;
 	if (cap == IOMMU_CAP_PRE_BOOT_PROTECTION)
 		return dmar_platform_optin();
+	if (cap == IOMMU_CAP_ENFORCE_CACHE_COHERENCY) {
+		struct device_domain_info *info = dev_iommu_priv_get(dev);
 
+		return ecap_sc_support(info->iommu->ecap);
+	}
 	return false;
 }
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 3c9da1f8979e3a..40cf2d8393465f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -108,6 +108,11 @@ enum iommu_cap {
 	IOMMU_CAP_NOEXEC,		/* IOMMU_NOEXEC flag */
 	IOMMU_CAP_PRE_BOOT_PROTECTION,	/* Firmware says it used the IOMMU for
 					   DMA protection and we should too */
+	/*
+	 * Per-device flag indicating if enforce_cache_coherency() will work on
+	 * this device.
+	 */
+	IOMMU_CAP_ENFORCE_CACHE_COHERENCY,
 };
 
 /* These are the possible reserved region types */
-- 
2.38.0