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From: tip-bot for Andy Lutomirski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, luto@kernel.org, gnomes@lxorguk.ukuu.org.uk,
	bp@alien8.de, fenghua.yu@intel.com, hpa@zytor.com,
	dave.hansen@linux.intel.com, torvalds@linux-foundation.org,
	oleg@redhat.com, linux-kernel@vger.kernel.org,
	tedheadster@gmail.com, mingo@kernel.org, bp@suse.de,
	yu-cheng.yu@intel.com, peterz@infradead.org, brgerst@gmail.com,
	riel@redhat.com
Subject: [tip:x86/fpu] x86/cpu: Re-apply forced caps every time CPU caps are re-read
Date: Wed, 25 Jan 2017 03:41:26 -0800
Message-ID: <tip-60d3450167433f2d099ce2869dc52dd9e7dc9b29@git.kernel.org> (raw)
In-Reply-To: <c817eb373d2c67c2c81413a70fc9b845fa34a37e.1484705016.git.luto@kernel.org>

Commit-ID:  60d3450167433f2d099ce2869dc52dd9e7dc9b29
Gitweb:     http://git.kernel.org/tip/60d3450167433f2d099ce2869dc52dd9e7dc9b29
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 18 Jan 2017 11:15:39 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 25 Jan 2017 10:12:41 +0100

x86/cpu: Re-apply forced caps every time CPU caps are re-read

Calling get_cpu_cap() will reset a bunch of CPU features.  This will
cause the system to lose track of force-set and force-cleared
features in the words that are reset until the end of CPU
initialization.  This can cause X86_FEATURE_FPU, for example, to
change back and forth during boot and potentially confuse CPU setup.

To minimize the chance of confusion, re-apply forced caps every time
get_cpu_cap() is called.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Whitehead <tedheadster@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/c817eb373d2c67c2c81413a70fc9b845fa34a37e.1484705016.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/common.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2ea16e0..d09b5ee 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -758,6 +758,13 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 		c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a);
 
 	init_scattered_cpuid_features(c);
+
+	/*
+	 * Clear/Set all flags overridden by options, after probe.
+	 * This needs to happen each time we re-probe, which may happen
+	 * several times during CPU initialization.
+	 */
+	apply_forced_caps(c);
 }
 
 static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)

  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-18 19:15 [PATCH v2 0/6] CPUID and FPU fixes Andy Lutomirski
2017-01-18 19:15 ` [PATCH v2 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read Andy Lutomirski
2017-01-19 11:23   ` Borislav Petkov
2017-01-25 11:41   ` tip-bot for Andy Lutomirski [this message]
2017-01-18 19:15 ` [PATCH v2 5/6] x86/fpu: Fix CPUID-less FPU detection Andy Lutomirski
2017-01-19 11:23   ` Borislav Petkov
2017-01-25 11:42   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 1/6] x86/cpu: Add X86_FEATURE_CPUID Andy Lutomirski
2017-01-25 11:40 ` [tip:x86/fpu] " tip-bot for Borislav Petkov
2017-01-18 19:15 [PATCH v2 2/6] x86/cpu: Factor out application of forced cpu caps Andy Lutomirski
2017-01-25 11:40 ` [tip:x86/fpu] x86/cpu: Factor out application of forced CPU caps tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 4/6] x86/fpu: Fix "x86/fpu: Legacy x87 FPU detected" message Andy Lutomirski
2017-01-25 11:42 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2017-01-18 19:15 [PATCH v2 6/6] x86/fpu: Fix the "Giving up, no FPU found" test Andy Lutomirski
2017-01-25 11:43 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski

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