linux-kernel - [PATCH] x86/cpufeatures: make bits in cpu_caps_cleared[] and cpu_cpus

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Date:   Wed, 18 Mar 2020 14:16:24 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     xiaoyao.li@...el.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] x86/cpufeatures: make bits in cpu_caps_cleared[] and cpu_cpus_set[] exclusive

In apply_forced_caps(), cpu_caps_set[] overrides cpu_caps_cleared[], so
that setup_clear_cpu_cap() cannot clear one cap if setup_force_cpu_cap()
sets the cap before it.

Explicitly clear the bit in cpu_caps_cleared[] when set it in
cpu_caps_set[], and vice versa, can fix this.

Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---
 arch/x86/include/asm/cpufeature.h | 1 +
 arch/x86/kernel/cpu/cpuid-deps.c  | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 59bf91c57aa8..f6d976b05d2c 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -144,6 +144,7 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
 #define setup_force_cpu_cap(bit) do { \
 	set_cpu_cap(&boot_cpu_data, bit);	\
 	set_bit(bit, (unsigned long *)cpu_caps_set);	\
+	clear_bit(bit, (unsigned long *)cpu_caps_cleared);	\
 } while (0)
 
 #define setup_force_cpu_bug(bit) setup_force_cpu_cap(bit)
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index 3cbe24ca80ab..e16c36094e6c 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -82,6 +82,7 @@ static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
 	if (!c) {
 		clear_cpu_cap(&boot_cpu_data, feature);
 		set_bit(feature, (unsigned long *)cpu_caps_cleared);
+		clear_bit(feature, (unsigned long *)cpu_caps_set);
 	} else {
 		clear_bit(feature, (unsigned long *)c->x86_capability);
 	}
-- 
2.20.1