linux-kernel - [PATCH 3/4] iommu/vt-d: Fix PASID directory pointer coherency

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Date:   Thu, 16 Feb 2023 21:08:15 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Tina Zhang <tina.zhang@...el.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] iommu/vt-d: Fix PASID directory pointer coherency

From: Jacob Pan <jacob.jun.pan@...ux.intel.com>

On platforms that do not support IOMMU Extended capability bit 0
Page-walk Coherency, CPU caches are not snooped when IOMMU is accessing
any translation structures. IOMMU access goes only directly to
memory. Intel IOMMU code was missing a flush for the PASID table
directory that resulted in the unrecoverable fault as shown below.

This patch adds clflush calls whenever allocating and updating
a PASID table directory to ensure cache coherency.

On the reverse direction, there's no need to clflush the PASID directory
pointer when we deactivate a context entry in that IOMMU hardware will
not see the old PASID directory pointer after we clear the context entry.
PASID directory entries are also never freed once allocated.

 DMAR: DRHD: handling fault status reg 3
 DMAR: [DMA Read NO_PASID] Request device [00:0d.2] fault addr 0x1026a4000
       [fault reason 0x51] SM: Present bit in Directory Entry is clear
 DMAR: Dump dmar1 table entries for IOVA 0x1026a4000
 DMAR: scalable mode root entry: hi 0x0000000102448001, low 0x0000000101b3e001
 DMAR: context entry: hi 0x0000000000000000, low 0x0000000101b4d401
 DMAR: pasid dir entry: 0x0000000101b4e001
 DMAR: pasid table entry[0]: 0x0000000000000109
 DMAR: pasid table entry[1]: 0x0000000000000001
 DMAR: pasid table entry[2]: 0x0000000000000000
 DMAR: pasid table entry[3]: 0x0000000000000000
 DMAR: pasid table entry[4]: 0x0000000000000000
 DMAR: pasid table entry[5]: 0x0000000000000000
 DMAR: pasid table entry[6]: 0x0000000000000000
 DMAR: pasid table entry[7]: 0x0000000000000000
 DMAR: PTE not present at level 4

Cc: <stable@...r.kernel.org>
Fixes: 0bbeb01a4faf ("iommu/vt-d: Manage scalalble mode PASID tables")
Reviewed-by: Kevin Tian <kevin.tian@...el.com>
Reported-by: Sukumar Ghorai <sukumar.ghorai@...el.com>
Signed-off-by: Ashok Raj <ashok.raj@...el.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Link: https://lore.kernel.org/r/20230209212843.1788125-1-jacob.jun.pan@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/intel/pasid.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
index fb3c7020028d..979f796175b1 100644
--- a/drivers/iommu/intel/pasid.c
+++ b/drivers/iommu/intel/pasid.c
@@ -128,6 +128,9 @@ int intel_pasid_alloc_table(struct device *dev)
 	pasid_table->max_pasid = 1 << (order + PAGE_SHIFT + 3);
 	info->pasid_table = pasid_table;
 
+	if (!ecap_coherent(info->iommu->ecap))
+		clflush_cache_range(pasid_table->table, size);
+
 	return 0;
 }
 
@@ -215,6 +218,10 @@ static struct pasid_entry *intel_pasid_get_entry(struct device *dev, u32 pasid)
 			free_pgtable_page(entries);
 			goto retry;
 		}
+		if (!ecap_coherent(info->iommu->ecap)) {
+			clflush_cache_range(entries, VTD_PAGE_SIZE);
+			clflush_cache_range(&dir[dir_index].val, sizeof(*dir));
+		}
 	}
 
 	return &entries[index];
-- 
2.34.1