linux-kernel - [PATCH] x86, cpu, amd: Use 8-bit extractor for NodeId field

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Message-ID: <1421691538-7152-1-git-send-email-Aravind.Gopalakrishnan@amd.com>
Date:	Mon, 19 Jan 2015 12:18:58 -0600
From:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
To:	<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<x86@...nel.org>, <bp@...e.de>, <riel@...hat.com>,
	<mgorman@...e.de>, <jolsa@...nel.org>, <pbonzini@...hat.com>,
	<jacob.w.shin@...il.com>, <linux-kernel@...r.kernel.org>
CC:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Subject: [PATCH] x86, cpu, amd: Use 8-bit extractor for NodeId field

The NodeId field in cpuid_ecx(0x8000001e) is a 8 bit field.
Although current extractor works fine, it will break if/when
the most significant 5 bits ever get used.

So, lets honor the field as architected in the BKDG

Reference: BKDG for AMD Fam15h Models 00h-0fh,
CPUID Fn8000_001E_ECX Node Identifiers

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
---
 arch/x86/kernel/cpu/amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a220239..9942b83 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -300,7 +300,7 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
 
 		cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
 		nodes = ((ecx >> 8) & 7) + 1;
-		node_id = ecx & 7;
+		node_id = ecx & 0xff;
 
 		/* get compute unit information */
 		smp_num_siblings = ((ebx >> 8) & 3) + 1;
-- 
1.9.1

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