[PATCH v4 01/17] 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.

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/amd/iommu.c   |  2 ++
 drivers/iommu/intel/iommu.c | 16 +++++++++++-----
 include/linux/iommu.h       |  5 +++++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 45299eb7e8e306..240c535e317cc7 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2278,6 +2278,8 @@ 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 f298e51d5aa67a..157c9727411076 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -4450,14 +4450,20 @@ static bool intel_iommu_enforce_cache_coherency(struct iommu_domain *domain)
 
 static bool intel_iommu_capable(struct device *dev, enum iommu_cap cap)
 {
-	if (cap == IOMMU_CAP_CACHE_COHERENCY)
+	struct device_domain_info *info = dev_iommu_priv_get(dev);
+
+	switch (cap) {
+	case IOMMU_CAP_CACHE_COHERENCY:
 		return true;
-	if (cap == IOMMU_CAP_INTR_REMAP)
+	case IOMMU_CAP_INTR_REMAP:
 		return irq_remapping_enabled == 1;
-	if (cap == IOMMU_CAP_PRE_BOOT_PROTECTION)
+	case IOMMU_CAP_PRE_BOOT_PROTECTION:
 		return dmar_platform_optin();
-
-	return false;
+	case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:
+		return ecap_sc_support(info->iommu->ecap);
+	default:
+		return false;
+	}
 }
 
 static struct iommu_device *intel_iommu_probe_device(struct device *dev)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 68d7d304cdb761..a09fd32d8cc273 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -124,6 +124,11 @@ 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 */
-- 
2.38.1