[RFC PATCH 5/5] iommu/amd: Provide kernel command line option to enable GAPPI

[Sairaj Kodilkar <sarunkod@amd.com>]

Enable GAPPI when IOMMU GAPPISup extended feature bit is set and
the kernel is booted with "amd_iommu=gappi" command line parameter.

Co-developed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Sairaj Kodilkar <sarunkod@amd.com>
---
 drivers/iommu/amd/amd_iommu_types.h |  2 ++
 drivers/iommu/amd/init.c            | 20 ++++++++++++++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 26d7a9796e64..de0b23306944 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -94,6 +94,7 @@
 #define FEATURE_X2APIC		BIT_ULL(2)
 #define FEATURE_NX		BIT_ULL(3)
 #define FEATURE_GT		BIT_ULL(4)
+#define FEATURE_GAPPI		BIT_ULL(5)
 #define FEATURE_IA		BIT_ULL(6)
 #define FEATURE_GA		BIT_ULL(7)
 #define FEATURE_HE		BIT_ULL(8)
@@ -191,6 +192,7 @@
 #define CONTROL_EPH_EN		45
 #define CONTROL_XT_EN		50
 #define CONTROL_INTCAPXT_EN	51
+#define CONTROL_GAPPI_EN	55
 #define CONTROL_GCR3TRPMODE	58
 #define CONTROL_IRTCACHEDIS	59
 #define CONTROL_SNPAVIC_EN	61
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 2e1889f8a9e4..b3e1d8ee7e9d 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3038,11 +3038,20 @@ static void enable_iommus_vapic(void)
 		return;
 	}
 
+	if (amd_iommu_gappi &&
+	    !(check_feature(FEATURE_GAPPI) &&
+	      AMD_IOMMU_GUEST_IR_VAPIC(amd_iommu_guest_ir))) {
+		pr_warn("GAPPI is not supported.\n");
+		amd_iommu_gappi = false;
+	}
+
 	/* Enabling GAM and SNPAVIC support */
 	for_each_iommu(iommu) {
-		if (iommu_init_ga_log(iommu) ||
-		    iommu_ga_log_enable(iommu))
-			return;
+		if (amd_iommu_gappi)
+			iommu_feature_enable(iommu, CONTROL_GAPPI_EN);
+		else if (iommu_init_ga_log(iommu) ||
+			 iommu_ga_log_enable(iommu))
+			 return;
 
 		iommu_feature_enable(iommu, CONTROL_GAM_EN);
 		if (amd_iommu_snp_en)
@@ -3050,7 +3059,8 @@ static void enable_iommus_vapic(void)
 	}
 
 	amd_iommu_irq_ops.capability |= (1 << IRQ_POSTING_CAP);
-	pr_info("Virtual APIC enabled\n");
+	pr_info("Virtual APIC enabled with %s\n",
+		amd_iommu_gappi ? "GAPPI" : "GALOG");
 #endif
 }
 
@@ -3741,6 +3751,8 @@ static int __init parse_amd_iommu_options(char *str)
 		} else if (strncmp(str, "v2_pgsizes_only", 15) == 0) {
 			pr_info("Restricting V1 page-sizes to 4KiB/2MiB/1GiB");
 			amd_iommu_pgsize_bitmap = AMD_IOMMU_PGSIZES_V2;
+		} else if (strncmp(str, "gappi", 5) == 0) {
+			amd_iommu_gappi = true;
 		} else {
 			pr_notice("Unknown option - '%s'\n", str);
 		}
-- 
2.34.1