linux-kernel - [PATCH 1/3] x86: Bugfix bit-rot in the calling of legacy_cache

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Date:	Tue, 30 Sep 2014 04:11:48 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	mingo@...hat.com, davej@...hat.com, hpa@...or.com,
	tglx@...utronix.de, hmh@....eng.br, x86@...nel.org
Cc:	linux-kernel@...r.kernel.org,
	Bryan O'Donoghue <pure.logic@...us-software.ie>
Subject: [PATCH 1/3] x86: Bugfix bit-rot in the calling of legacy_cache_size

legacy_cache_size is used by certain processors to report the
size of cache. Currently only X86_VENDOR_UNKNOWN could call
default_init() => cpu_detect_cache_sizes() => legacy_cache_size()

Make an update to identify_cpu to make an explicit call to default_init()
We want to do this since some processors that report vendor strings via
cpuid also want to run legacy_cache_size callbacks - which won't happen
since init_intel() init_amd() and friends take the place of default_init()
and don't themselves make explicit calls to legacy_cache_size.

Also current code has an
#ifdef CONFIG_X86_64
        cpu_detect_cache_sizes(c);
#endif

where cpu_detect_cache_sizes calls legacy_cache_size(); is typically
defined inside of a CONFIG_X86_32
#ifdef CONFIG_X86_32
        .legacy_cache_size = centaur_size_cache,
#endif
#ifdef CONFIG_X86_32
	.legacy_cache_size = intel_size_cache,
#endif
#ifdef CONFIG_X86_32
        .legacy_cache_size = amd_size_cache,
#endif

Signed-off-by: Bryan O'Donoghue <pure.logic@...us-software.ie>
---
 arch/x86/kernel/cpu/common.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index e4ab2b4..53a33fa 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -67,9 +67,8 @@ void __init setup_cpu_local_masks(void)
 
 static void default_init(struct cpuinfo_x86 *c)
 {
-#ifdef CONFIG_X86_64
 	cpu_detect_cache_sizes(c);
-#else
+
 	/* Not much we can do here... */
 	/* Check if at least it has cpuid */
 	if (c->cpuid_level == -1) {
@@ -79,7 +78,6 @@ static void default_init(struct cpuinfo_x86 *c)
 		else if (c->x86 == 3)
 			strcpy(c->x86_model_id, "386");
 	}
-#endif
 }
 
 static const struct cpu_dev default_cpu = {
@@ -874,6 +872,15 @@ static void identify_cpu(struct cpuinfo_x86 *c)
 #endif
 
 	/*
+	 * If c_x86_vendor != X86_VENDOR_UNKNOWN i.e. a known vendor then
+	 * there's a vendor specific c_init()
+	 *
+	 * Even still Intel, AMD and VIA make use of legacy_cache_size which
+	 * is reachable only through default_init right now
+	 */
+	if (this_cpu->c_x86_vendor != X86_VENDOR_UNKNOWN)
+		default_init(c);
+	/*
 	 * Vendor-specific initialization.  In this section we
 	 * canonicalize the feature flags, meaning if there are
 	 * features a certain CPU supports which CPUID doesn't
-- 
1.9.1

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