[PATCH 4/6] iommu/vt-d: Do deferred attachment in iommu_need_mapping()

[Tim Gardner]

From: Joerg Roedel <jroedel at suse.de>

BugLink: https://bugs.launchpad.net/bugs/1922738

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 at vger.kernel.org # v5.5
Reviewed-by: Jerry Snitselaar <jsnitsel at redhat.com>
Acked-by: Lu Baolu <baolu.lu at linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel at suse.de>
(cherry picked from commit a11bfde9c77df1fd350ea27169ab921f511bf5d0)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/iommu/intel-iommu.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d234cb22369e..94d88d7fc63c 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2459,9 +2459,6 @@ 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);
 }
 
@@ -3480,6 +3477,9 @@ 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;
@@ -3843,7 +3843,11 @@ bounce_map_single(struct device *dev, phys_addr_t paddr, size_t size,
 	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;
 
-- 
2.17.1