Re: [PATCH] [x86, msr]: execute on the correct CPU subset

[Borislav Petkov <borislav.petkov@amd.com>]

On Mon, Jul 27, 2009 at 01:46:26PM -0700, H. Peter Anvin wrote:
> Any reason not to use get_cpu() ... put_cpu() instead?

In case you haven't applied the one from yesterday yet, here's a better
one which uses struct cpumask * instead of cpumask_t.

--
From: Borislav Petkov <borislav.petkov@amd.com>
Date: Mon, 6 Jul 2009 16:08:34 +0200
Subject: [PATCH] [x86, msr]: execute on the correct CPU subset

rdmsr_on_cpus/wrmsr_on_cpus were erroneously executing on the current
CPU even in the case where it wasn't in the supplied bitmask. Add a
check for that and handle accordingly.

While at it, since rdmsr_on_cpus and wrmsr_on_cpus are almost identical,
fold them call into a common __rwmsr_on_cpus helper passing a function
pointer arg to the actual MSR operation.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
---
 arch/x86/include/asm/msr.h |    4 +-
 arch/x86/lib/msr.c         |   60 +++++++++++++++++---------------------------
 2 files changed, 25 insertions(+), 39 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 48ad9d2..988b067 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -224,8 +224,8 @@ do {                                                            \
 #ifdef CONFIG_SMP
 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);
-void rdmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs);
-void wrmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs);
+void rdmsr_on_cpus(struct cpumask *mask, u32 msr_no, struct msr *msrs);
+void wrmsr_on_cpus(struct cpumask *mask, u32 msr_no, struct msr *msrs);
 int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
 int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
 #else  /*  CONFIG_SMP  */
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index 1440b9c..da156b8 100644
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -71,14 +71,9 @@ int wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
 }
 EXPORT_SYMBOL(wrmsr_on_cpu);
 
-/* rdmsr on a bunch of CPUs
- *
- * @mask:       which CPUs
- * @msr_no:     which MSR
- * @msrs:       array of MSR values
- *
- */
-void rdmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs)
+static inline void __rwmsr_on_cpus(struct cpumask *mask, u32 msr_no,
+				   struct msr *msrs,
+				   void (*msr_func) (void *info))
 {
 	struct msr_info rv;
 	int this_cpu;
@@ -89,16 +84,25 @@ void rdmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs)
 	rv.msrs	  = msrs;
 	rv.msr_no = msr_no;
 
-	preempt_disable();
-	/*
-	 * FIXME: handle the CPU we're executing on separately for now until
-	 * smp_call_function_many has been fixed to not skip it.
-	 */
-	this_cpu = raw_smp_processor_id();
-	smp_call_function_single(this_cpu, __rdmsr_on_cpu, &rv, 1);
+	this_cpu = get_cpu();
 
-	smp_call_function_many(mask, __rdmsr_on_cpu, &rv, 1);
-	preempt_enable();
+	if (cpumask_test_cpu(this_cpu, mask))
+		msr_func(&rv);
+
+	smp_call_function_many(mask, msr_func, &rv, 1);
+	put_cpu();
+}
+
+/* rdmsr on a bunch of CPUs
+ *
+ * @mask:       which CPUs
+ * @msr_no:     which MSR
+ * @msrs:       array of MSR values
+ *
+ */
+void rdmsr_on_cpus(struct cpumask *mask, u32 msr_no, struct msr *msrs)
+{
+	__rwmsr_on_cpus(mask, msr_no, msrs, __rdmsr_on_cpu);
 }
 EXPORT_SYMBOL(rdmsr_on_cpus);
 
@@ -110,27 +114,9 @@ EXPORT_SYMBOL(rdmsr_on_cpus);
  * @msrs:       array of MSR values
  *
  */
-void wrmsr_on_cpus(const cpumask_t *mask, u32 msr_no, struct msr *msrs)
+void wrmsr_on_cpus(struct cpumask *mask, u32 msr_no, struct msr *msrs)
 {
-	struct msr_info rv;
-	int this_cpu;
-
-	memset(&rv, 0, sizeof(rv));
-
-	rv.off    = cpumask_first(mask);
-	rv.msrs   = msrs;
-	rv.msr_no = msr_no;
-
-	preempt_disable();
-	/*
-	 * FIXME: handle the CPU we're executing on separately for now until
-	 * smp_call_function_many has been fixed to not skip it.
-	 */
-	this_cpu = raw_smp_processor_id();
-	smp_call_function_single(this_cpu, __wrmsr_on_cpu, &rv, 1);
-
-	smp_call_function_many(mask, __wrmsr_on_cpu, &rv, 1);
-	preempt_enable();
+	__rwmsr_on_cpus(mask, msr_no, msrs, __wrmsr_on_cpu);
 }
 EXPORT_SYMBOL(wrmsr_on_cpus);
 
-- 
1.6.3.3

-- 
Regards/Gruss,
Boris.

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