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

Borislav Petkov
2009-07-28T10:30:10Z

On Mon, Jul 27, 2009 at 01:46:26PM -0700, H. Peter Anvin wrote:
> Borislav Petkov wrote:
> >
> > 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);
> >
> > - smp_call_function_many(mask, __rdmsr_on_cpu, &rv, 1);
> > + if (cpumask_test_cpu(this_cpu, mask))
> > + msr_func(&rv);
> > +
> > + smp_call_function_many(mask, msr_func, &rv, 1);
> > preempt_enable();
> > }
>
> Any reason not to use get_cpu() ... put_cpu() instead?

None, patch updated.

--
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/lib/msr.c | 58 +++++++++++++++++++--------------------------------
1 files changed, 22 insertions(+), 36 deletions(-)

diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index 1440b9c..cf879f0 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(const cpumask_t *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(const cpumask_t *mask, u32 msr_no, struct msr *msrs)
+{
+ __rwmsr_on_cpus(mask, msr_no, msrs, __rdmsr_on_cpu);
}
EXPORT_SYMBOL(rdmsr_on_cpus);

@@ -112,25 +116,7 @@ EXPORT_SYMBOL(rdmsr_on_cpus);
*/
void wrmsr_on_cpus(const cpumask_t *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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