linux-kernel - [PATCH v3 2/2] iommu/vt-d: Fix checks and print in pgtable

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Message-Id: <20241024092146.715063-3-zhenzhong.duan@intel.com>
Date: Thu, 24 Oct 2024 17:21:46 +0800
From: Zhenzhong Duan <zhenzhong.duan@...el.com>
To: iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Cc: dwmw2@...radead.org,
	baolu.lu@...ux.intel.com,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	chao.p.peng@...el.com,
	Zhenzhong Duan <zhenzhong.duan@...el.com>,
	Kyung Min Park <kyung.min.park@...el.com>
Subject: [PATCH v3 2/2] iommu/vt-d: Fix checks and print in pgtable_walk()

There are some issues in pgtable_walk():

1. Super page is dumped as non-present page
2. dma_pte_superpage() should not check against leaf page table entries
3. Pointer pte is never NULL so checking it is meaningless
4. When an entry is not present, it still makes sense to dump the entry
   content.

Fix 1,2 by checking dma_pte_superpage()'s returned value after level check.
Fix 3 by removing pte check.
Fix 4 by checking persent bit after printing.

By this chance, change to print "page table not present" instead of "PTE
not present" to be clearer.

Fixes: 914ff7719e8a ("iommu/vt-d: Dump DMAR translation structure when DMA fault occurs")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@...el.com>
---
 drivers/iommu/intel/iommu.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index e7a711a42528..6c9a69a89b81 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -707,14 +707,15 @@ static void pgtable_walk(struct intel_iommu *iommu, unsigned long pfn,
 	while (1) {
 		offset = pfn_level_offset(pfn, level);
 		pte = &parent[offset];
-		if (!pte || (dma_pte_superpage(pte) || !dma_pte_present(pte))) {
-			pr_info("PTE not present at level %d\n", level);
-			break;
-		}
 
 		pr_info("pte level: %d, pte value: 0x%016llx\n", level, pte->val);
 
-		if (level == 1)
+		if (!dma_pte_present(pte)) {
+			pr_info("page table not present at level %d\n", level - 1);
+			break;
+		}
+
+		if (level == 1 || dma_pte_superpage(pte))
 			break;
 
 		parent = phys_to_virt(dma_pte_addr(pte));
-- 
2.34.1