linux-kernel - [PATCH] Fix set apic mode from x2apic enabled bit patch

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Date:   Thu, 15 Apr 2021 17:06:26 -0500
From:   Mike Travis <mike.travis@....com>
To:     Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Steve Wahl <steve.wahl@....com>, x86@...nel.org
Cc:     Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <dimitri.sivanich@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Russ Anderson <russ.anderson@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Fix set apic mode from x2apic enabled bit patch

Do not set uv_system_type for hubless UV systems as it tricks the
is_uv_system function into thinking it's a UV hubbed system and includes
a UV HUB RTC.  This causes UV RTC init to panic on UV hubless systems.

Fixes: 41e2da9b5e67 ("x86/platform/uv: Use x2apic enabled bit as set by BIOS to indicate APIC mode")

[41e2da9b5e67 was accepted into tip x86/platform branch but not yet
pulled into the linus tree.]

Signed-off-by: Mike Travis <mike.travis@....com>
Reviewed-by: Steve Wahl <steve.wahl@....com>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@....com>
---
 arch/x86/kernel/apic/x2apic_uv_x.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c
index 2e99605f9a05..68ef9abc91f7 100644
--- a/arch/x86/kernel/apic/x2apic_uv_x.c
+++ b/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -413,9 +413,8 @@ static int __init uv_set_system_type(char *_oem_id, char *_oem_table_id)
 		else
 			uv_hubless_system |= 0x8;
 
-		/* Copy OEM Table ID and set APIC Mode */
+		/* Copy OEM Table ID */
 		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);
-- 
2.21.0