linux-kernel - [PATCH v3 5/7] iommu/amd: Set translation valid bit only when IO page tables are in use

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Message-ID: <20220622171131.11870-6-suravee.suthikulpanit@amd.com>
Date:   Wed, 22 Jun 2022 12:11:29 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>
CC:     <joro@...tes.org>, <robin.murphy@....com>, <ashish.kalra@....com>,
        <vasant.hegde@....com>, <thomas.lendacky@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v3 5/7] iommu/amd: Set translation valid bit only when IO page tables are in use

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@....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 c62fb4470519..f5695ccb7c81 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -2544,7 +2544,8 @@ 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 0792cd618dba..4f4571d3ff61 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -1563,7 +1563,14 @@ static void set_dte_entry(struct amd_iommu *iommu, u16 devid,
 	    (domain->flags & PD_GIOV_MASK))
 		pte_root |= DTE_FLAG_GIOV;
 
-	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];
 
@@ -1625,7 +1632,11 @@ 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