linux-kernel - [PATCH v4 10/17] x86/clearcpuid: Apply cleared feature bits that are forced set before

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Message-Id: <1551494711-213533-11-git-send-email-fenghua.yu@intel.com>
Date:   Fri,  1 Mar 2019 18:45:04 -0800
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "H Peter Anvin" <hpa@...or.com>,
        "Paolo Bonzini" <pbonzini@...hat.com>,
        "Dave Hansen" <dave.hansen@...el.com>,
        "Ashok Raj" <ashok.raj@...el.com>,
        "Peter Zijlstra" <peterz@...radead.org>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>,
        "Xiaoyao Li " <xiaoyao.li@...el.com>
Cc:     "linux-kernel" <linux-kernel@...r.kernel.org>,
        "x86" <x86@...nel.org>, kvm@...r.kernel.org,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH v4 10/17] x86/clearcpuid: Apply cleared feature bits that are forced set before

Some CPU feature bits are forced set and stored in cpuinfo_x86 before
handling clearcpuid options. To clear those bits from cpuinfo_x86,
apply_forced_cap() is called after handling the options.

Please note, apply_forced_cap() is called twice on boot CPU. But this code
is simple and there is no functionality issue.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 arch/x86/include/asm/cpu.h   | 2 ++
 arch/x86/kernel/cpu/common.c | 5 +++--
 arch/x86/kernel/fpu/init.c   | 2 ++
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index e241abce1a2a..487f32ecea0b 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -26,6 +26,8 @@ struct x86_cpu {
 	struct cpu cpu;
 };
 
+void apply_forced_caps(struct cpuinfo_x86 *c);
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern int arch_register_cpu(int num);
 extern void arch_unregister_cpu(int);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 79e7cc0c4c85..26723ea322fa 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -758,13 +758,14 @@ void cpu_detect(struct cpuinfo_x86 *c)
 	}
 }
 
-static void apply_forced_caps(struct cpuinfo_x86 *c)
+void apply_forced_caps(struct cpuinfo_x86 *c)
 {
 	int i;
 
 	for (i = 0; i < NCAPINTS + NBUGINTS; i++) {
-		c->x86_capability[i] &= ~cpu_caps_cleared[i];
+		/* Bits may be cleared after they are set. */
 		c->x86_capability[i] |= cpu_caps_set[i];
+		c->x86_capability[i] &= ~cpu_caps_cleared[i];
 	}
 }
 
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 99b895eea166..9c2801b605e3 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -5,6 +5,7 @@
 #include <asm/tlbflush.h>
 #include <asm/setup.h>
 #include <asm/cmdline.h>
+#include <asm/cpu.h>
 
 #include <linux/sched.h>
 #include <linux/sched/task.h>
@@ -261,6 +262,7 @@ static void __init clear_cpuid(void)
 		    bit >= 0 && bit < NCAPINTS * 32)
 			setup_clear_cpu_cap(bit);
 	}
+	apply_forced_caps(&boot_cpu_data);
 }
 
 /*
-- 
2.7.4