[PATCH] Use x2apic enabled bit as set by BIOS to indicate APIC mode

[Mike Travis <mike.travis@hpe.com>]

BIOS now sets the x2apic enabled bit (and the ACPI table) for extended
APIC modes.  Use that bit to indicate if extended mode is set.

Signed-off-by: Mike Travis <mike.travis@hpe.com>
---
 arch/x86/kernel/apic/x2apic_uv_x.c | 31 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 52bc217ca8c3..2e99605f9a05 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -369,6 +369,15 @@ static int __init early_get_arch_type(void)
 	return ret;
 }
 
+/* UV system found, check which APIC MODE BIOS already selected */
+static void __init early_set_apic_mode(void)
+{
+	if (x2apic_enabled())
+		uv_system_type = UV_X2APIC;
+	else
+		uv_system_type = UV_LEGACY_APIC;
+}
+
 static int __init uv_set_system_type(char *_oem_id, char *_oem_table_id)
 {
 	/* Save OEM_ID passed from ACPI MADT */
@@ -404,11 +413,13 @@ static int __init uv_set_system_type(char *_oem_id, char *_oem_table_id)
 		else
 			uv_hubless_system |= 0x8;
 
-		/* Copy APIC type */
+		/* Copy OEM Table ID and set APIC Mode */
 		uv_stringify(sizeof(oem_table_id), oem_table_id, _oem_table_id);
+		early_set_apic_mode();
 
 		pr_info("UV: OEM IDs %s/%s, SystemType %d, HUBLESS ID %x\n",
 			oem_id, oem_table_id, uv_system_type, uv_hubless_system);
+
 		return 0;
 	}
 
@@ -453,6 +464,7 @@ static int __init uv_set_system_type(char *_oem_id, char *_oem_table_id)
 	early_set_hub_type();
 
 	/* Other UV setup functions */
+	early_set_apic_mode();
 	early_get_pnodeid();
 	early_get_apic_socketid_shift();
 	x86_platform.is_untracked_pat_range = uv_is_untracked_pat_range;
@@ -472,29 +484,14 @@ static int __init uv_acpi_madt_oem_check(char *_oem_id, char *_oem_table_id)
 	if (uv_set_system_type(_oem_id, _oem_table_id) == 0)
 		return 0;
 
-	/* Save and Decode OEM Table ID */
+	/* Save for display of the OEM Table ID */
 	uv_stringify(sizeof(oem_table_id), oem_table_id, _oem_table_id);
 
-	/* This is the most common hardware variant, x2apic mode */
-	if (!strcmp(oem_table_id, "UVX"))
-		uv_system_type = UV_X2APIC;
-
-	/* Only used for very small systems, usually 1 chassis, legacy mode  */
-	else if (!strcmp(oem_table_id, "UVL"))
-		uv_system_type = UV_LEGACY_APIC;
-
-	else
-		goto badbios;
-
 	pr_info("UV: OEM IDs %s/%s, System/UVType %d/0x%x, HUB RevID %d\n",
 		oem_id, oem_table_id, uv_system_type, is_uv(UV_ANY),
 		uv_min_hub_revision_id);
 
 	return 0;
-
-badbios:
-	pr_err("UV: UVarchtype:%s not supported\n", uv_archtype);
-	BUG();
 }
 
 enum uv_system_type get_uv_system_type(void)
-- 
2.21.0