linux-kernel - [PATCH v2 3/3] iommu: amd: Re-purpose Exclusion range registers to support SNP CWWB

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Date:   Wed, 23 Sep 2020 12:13:47 +0000
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org
Cc:     joro@...tes.org, Jon.Grimm@....com, brijesh.singh@....com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH v2 3/3] iommu: amd: Re-purpose Exclusion range registers to support SNP CWWB

When the IOMMU SNP support bit is set in the IOMMU Extended Features
register, hardware re-purposes the following registers:

1. IOMMU Exclusion Base register (MMIO offset 0020h) to
   Completion Wait Write-Back (CWWB) Base register

2. IOMMU Exclusion Range Limit (MMIO offset 0028h) to
   Completion Wait Write-Back (CWWB) Range Limit register

and requires the IOMMU CWWB semaphore base and range to be programmed
in the register offset 0020h and 0028h accordingly.

Cc: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/amd_iommu_types.h |  1 +
 drivers/iommu/amd/init.c            | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 1e7966c73707..f696ac7c5f89 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -93,6 +93,7 @@
 #define FEATURE_PC		(1ULL<<9)
 #define FEATURE_GAM_VAPIC	(1ULL<<21)
 #define FEATURE_EPHSUP		(1ULL<<50)
+#define FEATURE_SNP		(1ULL<<63)
 
 #define FEATURE_PASID_SHIFT	32
 #define FEATURE_PASID_MASK	(0x1fULL << FEATURE_PASID_SHIFT)
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index febc072f2717..c55df4347487 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -359,6 +359,29 @@ static void iommu_set_exclusion_range(struct amd_iommu *iommu)
 			&entry, sizeof(entry));
 }
 
+static void iommu_set_cwwb_range(struct amd_iommu *iommu)
+{
+	u64 start = iommu_virt_to_phys((void *)iommu->cmd_sem);
+	u64 entry = start & PM_ADDR_MASK;
+
+	if (!iommu_feature(iommu, FEATURE_SNP))
+		return;
+
+	/* Note:
+	 * Re-purpose Exclusion base/limit registers for Completion wait
+	 * write-back base/limit.
+	 */
+	memcpy_toio(iommu->mmio_base + MMIO_EXCL_BASE_OFFSET,
+		    &entry, sizeof(entry));
+
+	/* Note:
+	 * Default to 4 Kbytes, which can be specified by setting base
+	 * address equal to the limit address.
+	 */
+	memcpy_toio(iommu->mmio_base + MMIO_EXCL_LIMIT_OFFSET,
+		    &entry, sizeof(entry));
+}
+
 /* Programs the physical address of the device table into the IOMMU hardware */
 static void iommu_set_device_table(struct amd_iommu *iommu)
 {
@@ -1901,6 +1924,9 @@ static int __init amd_iommu_init_pci(void)
 		ret = iommu_init_pci(iommu);
 		if (ret)
 			break;
+
+		/* Need to setup range after PCI init */
+		iommu_set_cwwb_range(iommu);
 	}
 
 	/*
-- 
2.17.1