linux-kernel - [PATCH] iommu: Implement deferred domain attachment

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Message-Id: <20200515094519.20338-1-joro@8bytes.org>
Date:   Fri, 15 May 2020 11:45:19 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Tom Murphy <murphyt7@....ie>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, jroedel@...e.de,
        Jerry Snitselaar <jsnitsel@...hat.com>
Subject: [PATCH] iommu: Implement deferred domain attachment

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

The IOMMU core code has support for deferring the attachment of a domain
to a device. This is needed in kdump kernels where the new domain must
not be attached to a device before the device driver takes it over.

But this needs support from the dma-ops code too, to actually do the
late attachment when there are DMA-API calls for the device. This got
lost in the AMD IOMMU driver after converting it to the dma-iommu code.

Do the late attachment in the dma-iommu code-path to fix the issue.

Cc: Jerry Snitselaar <jsnitsel@...hat.com>
Cc: Tom Murphy <murphyt7@....ie>
Reported-by: Jerry Snitselaar <jsnitsel@...hat.com>
Tested-by: Jerry Snitselaar <jsnitsel@...hat.com>
Fixes: be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api")
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/iommu.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4050569188be..f54ebb964271 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1889,13 +1889,19 @@ void iommu_domain_free(struct iommu_domain *domain)
 }
 EXPORT_SYMBOL_GPL(iommu_domain_free);
 
-static int __iommu_attach_device(struct iommu_domain *domain,
-				 struct device *dev)
+static bool __iommu_is_attach_deferred(struct iommu_domain *domain,
+				       struct device *dev)
+{
+	if (!domain->ops->is_attach_deferred)
+		return false;
+
+	return domain->ops->is_attach_deferred(domain, dev);
+}
+
+static int __iommu_attach_device_no_defer(struct iommu_domain *domain,
+					  struct device *dev)
 {
 	int ret;
-	if ((domain->ops->is_attach_deferred != NULL) &&
-	    domain->ops->is_attach_deferred(domain, dev))
-		return 0;
 
 	if (unlikely(domain->ops->attach_dev == NULL))
 		return -ENODEV;
@@ -1903,9 +1909,19 @@ static int __iommu_attach_device(struct iommu_domain *domain,
 	ret = domain->ops->attach_dev(domain, dev);
 	if (!ret)
 		trace_attach_device_to_domain(dev);
+
 	return ret;
 }
 
+static int __iommu_attach_device(struct iommu_domain *domain,
+				 struct device *dev)
+{
+	if (__iommu_is_attach_deferred(domain, dev))
+		return 0;
+
+	return __iommu_attach_device_no_defer(domain, dev);
+}
+
 int iommu_attach_device(struct iommu_domain *domain, struct device *dev)
 {
 	struct iommu_group *group;
@@ -2023,7 +2039,12 @@ EXPORT_SYMBOL_GPL(iommu_get_domain_for_dev);
  */
 struct iommu_domain *iommu_get_dma_domain(struct device *dev)
 {
-	return dev->iommu_group->default_domain;
+	struct iommu_domain *domain = dev->iommu_group->default_domain;
+
+	if (__iommu_is_attach_deferred(domain, dev))
+		__iommu_attach_device_no_defer(domain, dev);
+
+	return domain;
 }
 
 /*
-- 
2.25.1