linux-kernel - [PATCH 3/5] iommu/vt-d: Do deferred attachment in iommu_need

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Date:   Mon, 17 Feb 2020 20:38:56 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>
Cc:     Joerg Roedel <joro@...tes.org>, jroedel@...e.de,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/5] iommu/vt-d: Do deferred attachment in iommu_need_mapping()

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

The attachment of deferred devices needs to happen before the check
whether the device is identity mapped or not. Otherwise the check will
return wrong results, cause warnings boot failures in kdump kernels, like

	WARNING: CPU: 0 PID: 318 at ../drivers/iommu/intel-iommu.c:592 domain_get_iommu+0x61/0x70

	[...]

	 Call Trace:
	  __intel_map_single+0x55/0x190
	  intel_alloc_coherent+0xac/0x110
	  dmam_alloc_attrs+0x50/0xa0
	  ahci_port_start+0xfb/0x1f0 [libahci]
	  ata_host_start.part.39+0x104/0x1e0 [libata]

With the earlier check the kdump boot succeeds and a crashdump is written.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/intel-iommu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 42cdcce1602e..32f43695a22b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct device *dev)
 
 static struct dmar_domain *deferred_attach_domain(struct device *dev)
 {
-	if (unlikely(attach_deferred(dev)))
-		do_deferred_attach(dev);
-
 	return find_domain(dev);
 }
 
@@ -3595,6 +3592,9 @@ static bool iommu_need_mapping(struct device *dev)
 	if (iommu_dummy(dev))
 		return false;
 
+	if (unlikely(attach_deferred(dev)))
+		do_deferred_attach(dev);
+
 	ret = identity_mapping(dev);
 	if (ret) {
 		u64 dma_mask = *dev->dma_mask;
-- 
2.17.1