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

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Message-Id: <20241022095017.479081-3-zhenzhong.duan@intel.com>
Date: Tue, 22 Oct 2024 17:50:17 +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 2/2] iommu/vt-d: Fix checks in pgtable_walk()

It's not accurate to dump super page as non-present page,
meanwhile bit7 in first level page table entry is PAT bit,
also pointer pte is never NULL in pgtable_walk() context.

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 | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 8288b0ee7a61..fec5cc1147f3 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -707,14 +707,14 @@ 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))) {
+		if (!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 (level == 1 || dma_pte_superpage(pte))
 			break;
 
 		parent = phys_to_virt(dma_pte_addr(pte));
-- 
2.34.1