linux-kernel - [PATCH 2/2] iommu/vt-d: Make sure RMRRs are mapped before domain goes public

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Date:   Mon,  5 Sep 2016 13:02:30 +0200
From:   Joerg Roede <joro@...tes.org>
To:     David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 2/2] iommu/vt-d: Make sure RMRRs are mapped before domain goes public

From: Joerg Roedel <jroedel@...e.de>

When a domain is allocated through the get_valid_domain_for_dev
path, it will be context-mapped before the RMRR regions are
mapped in the page-table. This opens a short time window
where device-accesses to these regions fail and causing DMAR
faults.

Fix this by mapping the RMRR regions before the domain is
context-mapped.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/intel-iommu.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index bcdbe9d..a4407ea 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3428,17 +3428,18 @@ static unsigned long intel_alloc_iova(struct device *dev,
 
 static struct dmar_domain *__get_valid_domain_for_dev(struct device *dev)
 {
+	struct dmar_domain *domain, *tmp;
 	struct dmar_rmrr_unit *rmrr;
-	struct dmar_domain *domain;
 	struct device *i_dev;
 	int i, ret;
 
-	domain = get_domain_for_dev(dev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
-	if (!domain) {
-		pr_err("Allocating domain for %s failed\n",
-		       dev_name(dev));
-		return NULL;
-	}
+	domain = find_domain(dev);
+	if (domain)
+		goto out;
+
+	domain = find_or_alloc_domain(dev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
+	if (!domain)
+		goto out;
 
 	/* We have a new domain - setup possible RMRRs for the device */
 	rcu_read_lock();
@@ -3457,6 +3458,18 @@ static struct dmar_domain *__get_valid_domain_for_dev(struct device *dev)
 	}
 	rcu_read_unlock();
 
+	tmp = set_domain_for_dev(dev, domain);
+	if (!tmp || domain != tmp) {
+		domain_exit(domain);
+		domain = tmp;
+	}
+
+out:
+
+	if (!domain)
+		pr_err("Allocating domain for %s failed\n", dev_name(dev));
+
+
 	return domain;
 }
 
-- 
2.6.6