linux-kernel - [RFC PATCH 13/21] iommu/amd: Introduce vIOMMU command-line option

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Date:   Wed, 21 Jun 2023 18:55:00 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
        <kvm@...r.kernel.org>
CC:     <joro@...tes.org>, <robin.murphy@....com>, <yi.l.liu@...el.com>,
        <alex.williamson@...hat.com>, <jgg@...dia.com>,
        <nicolinc@...dia.com>, <baolu.lu@...ux.intel.com>,
        <eric.auger@...hat.com>, <pandoh@...gle.com>,
        <kumaranand@...gle.com>, <jon.grimm@....com>,
        <santosh.shukla@....com>, <vasant.hegde@....com>,
        <jay.chen@....com>, <joseph.chung@....com>,
        "Suravee Suthikulpanit" <suravee.suthikulpanit@....com>
Subject: [RFC PATCH 13/21] iommu/amd: Introduce vIOMMU command-line option

To disable vIOMMU feature, specify option "amd_iommu=viommu_disable".

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/amd_iommu.h       |  2 ++
 drivers/iommu/amd/amd_iommu_types.h |  1 +
 drivers/iommu/amd/init.c            | 10 ++++++++++
 3 files changed, 13 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index c9dfa4734801..a65d22384ab8 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -46,6 +46,8 @@ void amd_iommu_debugfs_setup(struct amd_iommu *iommu);
 static inline void amd_iommu_debugfs_setup(struct amd_iommu *iommu) {}
 #endif
 
+extern bool amd_iommu_viommu;
+
 /* Needed for interrupt remapping */
 extern int amd_iommu_prepare(void);
 extern int amd_iommu_enable(void);
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index aa16a7079b5c..019a9182df87 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -96,6 +96,7 @@
 #define FEATURE_GAM_VAPIC	(1ULL<<21)
 #define FEATURE_GIOSUP		(1ULL<<48)
 #define FEATURE_EPHSUP		(1ULL<<50)
+#define FEATURE_VIOMMU		(1ULL<<55)
 #define FEATURE_SNP		(1ULL<<63)
 
 #define FEATURE_GATS_5LEVEL	1ULL
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 6a045a187971..4dd9f09e16c4 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -194,6 +194,9 @@ bool amdr_ivrs_remap_support __read_mostly;
 
 bool amd_iommu_force_isolation __read_mostly;
 
+/* VIOMMU enabling flag */
+bool amd_iommu_viommu = true;
+
 /*
  * AMD IOMMU allows up to 2^16 different protection domains. This is a bitmap
  * to know which ones are already in use.
@@ -2154,6 +2157,9 @@ static void print_iommu_info(void)
 			if (iommu->features & FEATURE_SNP)
 				pr_cont(" SNP");
 
+			if (iommu->features & FEATURE_VIOMMU)
+				pr_cont(" vIOMMU");
+
 			pr_cont("\n");
 		}
 	}
@@ -2166,6 +2172,8 @@ static void print_iommu_info(void)
 		pr_info("V2 page table enabled (Paging mode : %d level)\n",
 			amd_iommu_gpt_level);
 	}
+	if (amd_iommu_viommu)
+		pr_info("AMD-Vi: vIOMMU enabled\n");
 }
 
 static int __init amd_iommu_init_pci(void)
@@ -3402,6 +3410,8 @@ static int __init parse_amd_iommu_options(char *str)
 			amd_iommu_pgtable = AMD_IOMMU_V1;
 		} else if (strncmp(str, "pgtbl_v2", 8) == 0) {
 			amd_iommu_pgtable = AMD_IOMMU_V2;
+		} else if (strncmp(str, "viommu_disable", 14) == 0) {
+			amd_iommu_viommu = false;
 		} else {
 			pr_notice("Unknown option - '%s'\n", str);
 		}
-- 
2.34.1