linux-kernel - [PATCH v2 2/2] iommu/vt-d: Remove rmrr check in domain attaching device path

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Date:   Thu, 13 Jul 2023 12:32:48 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Nicolin Chen <nicolinc@...dia.com>
Cc:     iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Lu Baolu <baolu.lu@...ux.intel.com>,
        Jason Gunthorpe <jgg@...dia.com>
Subject: [PATCH v2 2/2] iommu/vt-d: Remove rmrr check in domain attaching device path

The core code now prevents devices with RMRR regions from being assigned
to user space. There is no need to check for this condition in individual
drivers. Remove it to avoid duplicate code.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
---
 drivers/iommu/intel/iommu.c | 58 -------------------------------------
 1 file changed, 58 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 5c8c5cdc36cf..43a28bc60ce1 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2446,30 +2446,6 @@ static int dmar_domain_attach_device(struct dmar_domain *domain,
 	return 0;
 }
 
-static bool device_has_rmrr(struct device *dev)
-{
-	struct dmar_rmrr_unit *rmrr;
-	struct device *tmp;
-	int i;
-
-	rcu_read_lock();
-	for_each_rmrr_units(rmrr) {
-		/*
-		 * Return TRUE if this RMRR contains the device that
-		 * is passed in.
-		 */
-		for_each_active_dev_scope(rmrr->devices,
-					  rmrr->devices_cnt, i, tmp)
-			if (tmp == dev ||
-			    is_downstream_to_pci_bridge(dev, tmp)) {
-				rcu_read_unlock();
-				return true;
-			}
-	}
-	rcu_read_unlock();
-	return false;
-}
-
 /**
  * device_rmrr_is_relaxable - Test whether the RMRR of this device
  * is relaxable (ie. is allowed to be not enforced under some conditions)
@@ -2499,34 +2475,6 @@ static bool device_rmrr_is_relaxable(struct device *dev)
 		return false;
 }
 
-/*
- * There are a couple cases where we need to restrict the functionality of
- * devices associated with RMRRs.  The first is when evaluating a device for
- * identity mapping because problems exist when devices are moved in and out
- * of domains and their respective RMRR information is lost.  This means that
- * a device with associated RMRRs will never be in a "passthrough" domain.
- * The second is use of the device through the IOMMU API.  This interface
- * expects to have full control of the IOVA space for the device.  We cannot
- * satisfy both the requirement that RMRR access is maintained and have an
- * unencumbered IOVA space.  We also have no ability to quiesce the device's
- * use of the RMRR space or even inform the IOMMU API user of the restriction.
- * We therefore prevent devices associated with an RMRR from participating in
- * the IOMMU API, which eliminates them from device assignment.
- *
- * In both cases, devices which have relaxable RMRRs are not concerned by this
- * restriction. See device_rmrr_is_relaxable comment.
- */
-static bool device_is_rmrr_locked(struct device *dev)
-{
-	if (!device_has_rmrr(dev))
-		return false;
-
-	if (device_rmrr_is_relaxable(dev))
-		return false;
-
-	return true;
-}
-
 /*
  * Return the required default domain type for a specific device.
  *
@@ -4139,12 +4087,6 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
 	struct device_domain_info *info = dev_iommu_priv_get(dev);
 	int ret;
 
-	if (domain->type == IOMMU_DOMAIN_UNMANAGED &&
-	    device_is_rmrr_locked(dev)) {
-		dev_warn(dev, "Device is ineligible for IOMMU domain attach due to platform RMRR requirement.  Contact your platform vendor.\n");
-		return -EPERM;
-	}
-
 	if (info->domain)
 		device_block_translation(dev);
 
-- 
2.34.1