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Date:   Sat,  2 Oct 2021 18:10:12 +0530
From:   Ajay Garg <>
Cc:     Ajay Garg <>
Subject: [PATCH] iommu: intel: remove flooding of non-error logs, when new-DMA-PTE is the same as old-DMA-PTE.

Taking a SD-MMC controller (over PCI) as an example, following is an
example sequencing, where the log-flooding happened :

We have a host and a guest, both running latest x86_64 kernels.

Host-machine is booted up (with intel_iommu=on), and the DMA-PTEs
are setup for the controller (on the host), for the first time.

The SD-controller device is added to a (L1) guest on a KVM-VM
(via virt-manager).

The KVM-VM is booted up.

Above triggers a re-setup of DMA-PTEs on the host, for a
second time.

It is observed that the new PTEs formed (on the host) are same
as the original PTEs, and thus following logs, accompanied by
stacktraces, overwhelm the logs :

 DMAR: ERROR: DMA PTE for vPFN 0x428ec already set (to 3f6ec003 not 3f6ec003)
 DMAR: ERROR: DMA PTE for vPFN 0x428ed already set (to 3f6ed003 not 3f6ed003)
 DMAR: ERROR: DMA PTE for vPFN 0x428ee already set (to 3f6ee003 not 3f6ee003)
 DMAR: ERROR: DMA PTE for vPFN 0x428ef already set (to 3f6ef003 not 3f6ef003)
 DMAR: ERROR: DMA PTE for vPFN 0x428f0 already set (to 3f6f0003 not 3f6f0003)

As the PTEs are same, so there is no cause of concern, and we can easily
avoid the logs-flood for this non-error case.

Signed-off-by: Ajay Garg <>
 drivers/iommu/intel/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d75f59ae28e6..8bea8b4e3ff9 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -2370,7 +2370,7 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 		 * touches the iova range
 		tmp = cmpxchg64_local(&pte->val, 0ULL, pteval);
-		if (tmp) {
+		if (tmp && (tmp != pteval)) {
 			static int dumps = 5;
 			pr_crit("ERROR: DMA PTE for vPFN 0x%lx already set (to %llx not %llx)\n",
 				iov_pfn, tmp, (unsigned long long)pteval);

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