[PATCH 4/7] iommu/amd: Set translation valid bit only when IO page tables are in use

[Suravee Suthikulpanit via iommu <iommu@lists.linux-foundation.org>]

On AMD system with SNP enabled, IOMMU hardware checks the host translation
valid (TV) and guest translation valid (GV) bits in the device table entry
(DTE) before accessing the corresponded page tables.

However, current IOMMU driver sets the TV bit for all devices regardless
of whether the host page table is in use. This results in
ILLEGAL_DEV_TABLE_ENTRY event for devices, which do not the host page
table root pointer set up.

Thefore, when SNP is enabled, only set TV bit when DMA remapping is not
used, which is when domain ID in the AMD IOMMU device table entry (DTE)
is zero.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 drivers/iommu/amd/init.c  |  3 ++-
 drivers/iommu/amd/iommu.c | 15 +++++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index da32e7bdd1fa..a9152d3f33bf 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -2546,7 +2546,8 @@ static void init_device_table_dma(struct amd_iommu_pci_seg *pci_seg)
 
 	for (devid = 0; devid <= pci_seg->last_bdf; ++devid) {
 		__set_dev_entry_bit(dev_table, devid, DEV_ENTRY_VALID);
-		__set_dev_entry_bit(dev_table, devid, DEV_ENTRY_TRANSLATION);
+		if (!amd_iommu_snp_en)
+			__set_dev_entry_bit(dev_table, devid, DEV_ENTRY_TRANSLATION);
 	}
 }
 
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index b9dc0d4b6d77..ca4647f04382 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1552,7 +1552,14 @@ static void set_dte_entry(struct amd_iommu *iommu, u16 devid,
 
 	pte_root |= (domain->iop.mode & DEV_ENTRY_MODE_MASK)
 		    << DEV_ENTRY_MODE_SHIFT;
-	pte_root |= DTE_FLAG_IR | DTE_FLAG_IW | DTE_FLAG_V | DTE_FLAG_TV;
+	pte_root |= DTE_FLAG_IR | DTE_FLAG_IW | DTE_FLAG_V;
+
+	/*
+	 * When SNP is enabled, Only set TV bit when IOMMU
+	 * page translation is in use.
+	 */
+	if (!amd_iommu_snp_en || (domain->id != 0))
+		pte_root |= DTE_FLAG_TV;
 
 	flags = dev_table[devid].data[1];
 
@@ -1612,7 +1619,11 @@ static void clear_dte_entry(struct amd_iommu *iommu, u16 devid)
 	struct dev_table_entry *dev_table = get_dev_table(iommu);
 
 	/* remove entry from the device table seen by the hardware */
-	dev_table[devid].data[0]  = DTE_FLAG_V | DTE_FLAG_TV;
+	dev_table[devid].data[0]  = DTE_FLAG_V;
+
+	if (!amd_iommu_snp_en)
+		dev_table[devid].data[0] |= DTE_FLAG_TV;
+
 	dev_table[devid].data[1] &= DTE_FLAG_MASK;
 
 	amd_iommu_apply_erratum_63(iommu, devid);
-- 
2.32.0

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