linux-kernel - [PATCH 1/2] iommu/amd: Add support to indicate whether DMA remap support is enabled

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Date:   Tue, 15 Mar 2022 11:24:54 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Joerg Roedel <joro@...tes.org>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:     Will Deacon <will@...nel.org>,
        Andreas Noever <andreas.noever@...il.com>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:THUNDERBOLT DRIVER" <linux-usb@...r.kernel.org>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH 1/2] iommu/amd: Add support to indicate whether DMA remap support is enabled

Bit 1 of the IVFS IVInfo field indicates that IOMMU has been used for
pre-boot DMA protection.  Export this information to the kernel to
allow other drivers to use it.

Link: https://www.amd.com/system/files/TechDocs/48882_IOMMU.pdf
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/iommu/amd/amd_iommu_types.h |  1 +
 drivers/iommu/amd/init.c            | 18 ++++++++++++++++++
 include/linux/amd-iommu.h           |  5 +++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 47108ed44fbb..68e51213f119 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -407,6 +407,7 @@
 /* IOMMU IVINFO */
 #define IOMMU_IVINFO_OFFSET     36
 #define IOMMU_IVINFO_EFRSUP     BIT(0)
+#define IOMMU_IVINFO_DMA_REMAP  BIT(1)
 
 /* IOMMU Feature Reporting Field (for IVHD type 10h */
 #define IOMMU_FEAT_GASUP_SHIFT	6
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 7bfe37e52e21..e9b669592dfc 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -182,6 +182,7 @@ u32 amd_iommu_max_pasid __read_mostly = ~0;
 
 bool amd_iommu_v2_present __read_mostly;
 static bool amd_iommu_pc_present __read_mostly;
+static bool amdr_ivrs_remap_support __read_mostly;
 
 bool amd_iommu_force_isolation __read_mostly;
 
@@ -326,6 +327,8 @@ static void __init early_iommu_features_init(struct amd_iommu *iommu,
 {
 	if (amd_iommu_ivinfo & IOMMU_IVINFO_EFRSUP)
 		iommu->features = h->efr_reg;
+	if (amd_iommu_ivinfo & IOMMU_IVINFO_DMA_REMAP)
+		amdr_ivrs_remap_support = true;
 }
 
 /* Access to l1 and l2 indexed register spaces */
@@ -3269,6 +3272,21 @@ struct amd_iommu *get_amd_iommu(unsigned int idx)
 	return NULL;
 }
 
+/*
+ * ivrs_remap_support - Is %IOMMU_IVINFO_DMA_REMAP set in IVRS table
+ *
+ * Returns true if the platform has %IOMMU_IVINFO_DMA_REMAP% set in the IOMMU
+ * IVRS IVInfo field.
+ * Presence of this flag indicates to the OS/HV that the IOMMU is used for
+ * Preboot DMA protection and device accessed memory should be remapped after
+ * the OS has loaded.
+ */
+bool amd_ivrs_remap_support(void)
+{
+	return amdr_ivrs_remap_support;
+}
+EXPORT_SYMBOL_GPL(amd_ivrs_remap_support);
+
 /****************************************************************************
  *
  * IOMMU EFR Performance Counter support functionality. This code allows
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 58e6c3806c09..d07b9fed6474 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h
@@ -170,6 +170,7 @@ amd_iommu_update_ga(int cpu, bool is_run, void *data);
 
 extern int amd_iommu_activate_guest_mode(void *data);
 extern int amd_iommu_deactivate_guest_mode(void *data);
+extern bool amd_ivrs_remap_support(void);
 
 #else /* defined(CONFIG_AMD_IOMMU) && defined(CONFIG_IRQ_REMAP) */
 
@@ -194,6 +195,10 @@ static inline int amd_iommu_deactivate_guest_mode(void *data)
 {
 	return 0;
 }
+static inline bool amd_ivrs_remap_support(void)
+{
+	return false;
+}
 #endif /* defined(CONFIG_AMD_IOMMU) && defined(CONFIG_IRQ_REMAP) */
 
 int amd_iommu_get_num_iommus(void);
-- 
2.34.1