From: Joerg Roedel <jroedel@suse.de>
Date: Mon, 17 Feb 2020 17:20:59 +0100
Subject: iommu/vt-d: Do deferred attachment in iommu_need_mapping()
Git-commit: a11bfde9c77df1fd350ea27169ab921f511bf5d0
References: bsc#1159594
Patch-mainline: v5.6-rc3

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.

Fixes: 1ee0186b9a12 ("iommu/vt-d: Refactor find_domain() helper")
Cc: stable@vger.kernel.org # v5.5
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/intel-iommu.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2541,9 +2541,6 @@ static void do_deferred_attach(struct de
 
 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 de
 	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;
@@ -3958,7 +3958,11 @@ bounce_map_single(struct device *dev, ph
 	int prot = 0;
 	int ret;
 
+	if (unlikely(attach_deferred(dev)))
+		do_deferred_attach(dev);
+
 	domain = deferred_attach_domain(dev);
+
 	if (WARN_ON(dir == DMA_NONE || !domain))
 		return DMA_MAPPING_ERROR;