linux-kernel - [PATCH 1/3] iommu/amd: Introduce helper function to check feature bit on all IOMMUs

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Date:   Fri, 20 Aug 2021 15:29:55 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org
Cc:     joro@...tes.org, Jon.Grimm@....com, wei.huang2@....com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH 1/3] iommu/amd: Introduce helper function to check feature bit on all IOMMUs

IOMMU advertises feature via Extended Features Register (EFR).
The helper function checks if the specified feature bit is set
across all IOMMUs.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 drivers/iommu/amd/init.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 46280e6e1535..c97961451ac5 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -298,6 +298,19 @@ int amd_iommu_get_num_iommus(void)
 	return amd_iommus_present;
 }
 
+static bool check_feature_on_all_iommus(u64 mask)
+{
+	bool ret = false;
+	struct amd_iommu *iommu;
+
+	for_each_iommu(iommu) {
+		ret = iommu_feature(iommu, mask);
+		if (!ret)
+			return false;
+	}
+
+	return true;
+}
 /*
  * For IVHD type 0x11/0x40, EFR is also available via IVHD.
  * Default to IVHD EFR since it is available sooner
-- 
2.17.1