linux-kernel - [PATCH] iommu/vt-d: Do not dump pasid table entries in kdump kernel

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Message-Id: <1642583260-21095-1-git-send-email-zelin.deng@linux.alibaba.com>
Date:   Wed, 19 Jan 2022 17:07:40 +0800
From:   Zelin Deng <zelin.deng@...ux.alibaba.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Kyung Min Park <kyung.min.park@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/vt-d: Do not dump pasid table entries in kdump kernel

In kdump kernel PASID translations won't be copied from previous kernel
even if scalable-mode is enabled, so pages of PASID translations are
non-present in kdump kernel. Attempt to access those address will cause
PF fault:

[   13.396476] DMAR: DRHD: handling fault status reg 3
[   13.396478] DMAR: [DMA Read NO_PASID] Request device [81:00.0] fault addr 0xffffd000 [fault reason 0x59] SM: Present bit in PA$
[   13.396480] DMAR: Dump dmar5 table entries for IOVA 0xffffd000
[   13.396481] DMAR: scalable mode root entry: hi 0x0000000000000000, low 0x00000000460d1001
[   13.396482] DMAR: context entry: hi 0x0000000000000008, low 0x00000010c4237401
[   13.396485] BUG: unable to handle page fault for address: ff110010c4237000
[   13.396486] #PF: supervisor read access in kernel mode
[   13.396487] #PF: error_code(0x0000) - not-present page
[   13.396488] PGD 5d201067 P4D 5d202067 PUD 0
[   13.396490] Oops: 0000 [#1] PREEMPT SMP NOPTI
[   13.396491] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.16.0-rc6-next-20211224+ #6
[   13.396493] Hardware name: Intel Corporation EAGLESTREAM/EAGLESTREAM, BIOS EGSDCRB1.86B.0067.D12.2110190950 10/19/2021
[   13.396494] RIP: 0010:dmar_fault_dump_ptes+0x13b/0x295

Hence skip dumping pasid table entries if in kdump kernel.

Fixes: 914ff7719e8a (“iommu/vt-d: Dump DMAR translation structure when DMA fault occurs”)
Signed-off-by: Zelin Deng <zelin.deng@...ux.alibaba.com>
---
 drivers/iommu/intel/iommu.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 92fea3fb..f0134cf 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1074,6 +1074,12 @@ void dmar_fault_dump_ptes(struct intel_iommu *iommu, u16 source_id,
 	if (!sm_supported(iommu))
 		goto pgtable_walk;
 
+	/* PASID translations is not copied, skip dumping pasid table entries
+	 * otherwise non-present page will be accessed.
+	 */
+	if (is_kdump_kernel())
+		goto pgtable_walk;
+
 	/* get the pointer to pasid directory entry */
 	dir = phys_to_virt(ctx_entry->lo & VTD_PAGE_MASK);
 	if (!dir) {
-- 
1.8.3.1