linux-kernel - [PATCH V3 1/2] x86/msr: add msr_set/clear_bit_on

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Date:   Mon, 27 Mar 2017 11:30:47 -0700
From:   kan.liang@...el.com
To:     peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     bp@...en8.de, acme@...nel.org, eranian@...gle.com,
        jolsa@...nel.org, ak@...ux.intel.com,
        Kan Liang <Kan.liang@...el.com>
Subject: [PATCH V3 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions

From: Kan Liang <Kan.liang@...el.com>

To flip a MSR bit on many CPUs or specific CPU, currently it has to do
read-modify-write operation on the MSR through rd/wrmsr_on_cpu(s).
It actually sends two IPIs to the given CPU.

It is necessory to extend the single operation - msr_set/clear_bit - on
many CPUs or given CPU. It only sends one IPI to the given CPU, and
simplify MSR content manipulation.
The new functions wrap the smp_call_function* boilerplate code.

Signed-off-by: Kan Liang <Kan.liang@...el.com>
---
 arch/x86/include/asm/msr.h | 25 +++++++++++++++
 arch/x86/lib/msr-smp.c     | 76 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 898dba2..bfd83ab 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -25,6 +25,7 @@ struct msr_info {
 	struct msr reg;
 	struct msr *msrs;
 	int err;
+	u8 bit;
 };
 
 struct msr_regs_info {
@@ -314,6 +315,10 @@ int msr_set_bit(u32 msr, u8 bit);
 int msr_clear_bit(u32 msr, u8 bit);
 
 #ifdef CONFIG_SMP
+int msr_set_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit);
+int msr_clear_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit);
+void msr_set_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit);
+void msr_clear_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit);
 int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
 int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
 int rdmsrl_on_cpu(unsigned int cpu, u32 msr_no, u64 *q);
@@ -327,6 +332,26 @@ int wrmsrl_safe_on_cpu(unsigned int cpu, u32 msr_no, u64 q);
 int rdmsr_safe_regs_on_cpu(unsigned int cpu, u32 regs[8]);
 int wrmsr_safe_regs_on_cpu(unsigned int cpu, u32 regs[8]);
 #else  /*  CONFIG_SMP  */
+static inline int msr_set_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit)
+{
+	return msr_set_bit(msr, bit);
+}
+
+static inline int msr_clear_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit)
+{
+	return msr_clear_bit(msr, bit);
+}
+
+static inline void msr_set_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit)
+{
+	msr_set_bit(msr, bit);
+}
+
+static inline void msr_clear_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit)
+{
+	msr_clear_bit(msr, bit);
+}
+
 static inline int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 {
 	rdmsr(msr_no, *l, *h);
diff --git a/arch/x86/lib/msr-smp.c b/arch/x86/lib/msr-smp.c
index ce68b6a..8e704d9 100644
--- a/arch/x86/lib/msr-smp.c
+++ b/arch/x86/lib/msr-smp.c
@@ -3,6 +3,82 @@
 #include <linux/smp.h>
 #include <asm/msr.h>
 
+static void __msr_set_bit_on_cpu(void *info)
+{
+	struct msr_info *bit_info = info;
+
+	msr_set_bit(bit_info->msr_no, bit_info->bit);
+}
+
+static void __msr_clear_bit_on_cpu(void *info)
+{
+	struct msr_info *bit_info = info;
+
+	msr_clear_bit(bit_info->msr_no, bit_info->bit);
+}
+
+int msr_set_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit)
+{
+	struct msr_info info;
+	int err;
+
+	info.msr_no = msr;
+	info.bit = bit;
+
+	err = smp_call_function_single(cpu, __msr_set_bit_on_cpu, &info, 1);
+
+	return err;
+}
+EXPORT_SYMBOL(msr_set_bit_on_cpu);
+
+int msr_clear_bit_on_cpu(unsigned int cpu, u32 msr, u8 bit)
+{
+	struct msr_info info;
+	int err;
+
+	info.msr_no = msr;
+	info.bit = bit;
+
+	err = smp_call_function_single(cpu, __msr_clear_bit_on_cpu, &info, 1);
+
+	return err;
+}
+EXPORT_SYMBOL(msr_clear_bit_on_cpu);
+
+void msr_set_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit)
+{
+	struct msr_info info;
+	int this_cpu;
+
+	info.msr_no = msr;
+	info.bit = bit;
+
+	this_cpu = get_cpu();
+	if (cpumask_test_cpu(this_cpu, mask))
+		__msr_set_bit_on_cpu(&info);
+
+	smp_call_function_many(mask, __msr_set_bit_on_cpu, &info, 1);
+	put_cpu();
+}
+EXPORT_SYMBOL(msr_set_bit_on_cpus);
+
+void msr_clear_bit_on_cpus(const struct cpumask *mask, u32 msr, u8 bit)
+{
+	struct msr_info info;
+	int this_cpu;
+
+	info.msr_no = msr;
+	info.bit = bit;
+
+	this_cpu = get_cpu();
+	if (cpumask_test_cpu(this_cpu, mask))
+		__msr_clear_bit_on_cpu(&info);
+
+	smp_call_function_many(mask, __msr_clear_bit_on_cpu, &info, 1);
+	put_cpu();
+}
+EXPORT_SYMBOL(msr_clear_bit_on_cpus);
+
 static void __rdmsr_on_cpu(void *info)
 {
 	struct msr_info *rv = info;
-- 
2.7.4