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From: Andy Lutomirski <luto@kernel.org>
To: X86 ML <x86@kernel.org>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
	Borislav Petkov <bp@alien8.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Brian Gerst <brgerst@gmail.com>,
	Matthew Whitehead <tedheadster@gmail.com>,
	Andy Lutomirski <luto@kernel.org>
Subject: [PATCH v2 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read
Date: Wed, 18 Jan 2017 11:15:39 -0800
Message-ID: <c817eb373d2c67c2c81413a70fc9b845fa34a37e.1484705016.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1484705016.git.luto@kernel.org>

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
featueres 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>
---
 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 337eac606f39..8efe6e77f91d 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -757,6 +757,13 @@ 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)
-- 
2.9.3

  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 ` Andy Lutomirski [this message]
2017-01-19 11:23   ` [PATCH v2 3/6] x86/cpu: Re-apply forced caps every time cpu caps are re-read Borislav Petkov
2017-01-25 11:41   ` [tip:x86/fpu] x86/cpu: Re-apply forced caps every time CPU " tip-bot for Andy Lutomirski
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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