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authorAlexey Dobriyan <adobriyan@openvz.org>2007-02-16 01:48:11 -0800
committerDave Jones <davej@redhat.com>2007-02-20 14:23:43 -0500
commitb077ffb3b767c3efb44d00b998385a9cb127255c (patch)
tree160369b5541142afedc20a97a9c89718550cf2a3 /arch/i386
parent22f7bb0329a506f2fd61c14ce3c8bc632e08c732 (diff)
rdmsr_on_cpu, wrmsr_on_cpu
There was OpenVZ specific bug rendering some cpufreq drivers unusable on SMP. In short, when cpufreq code thinks it confined itself to needed cpu by means of set_cpus_allowed() to execute rdmsr, some "virtual cpu" feature can migrate process to anywhere. This triggers bugons and does wrong things in general. This got fixed by introducing rdmsr_on_cpu and wrmsr_on_cpu executing rdmsr and wrmsr on given physical cpu by means of smp_call_function_single(). Dave Jones mentioned cpufreq might be not only user of rdmsr_on_cpu() and wrmsr_on_cpu(), so I'm putting them into arch/{i386,x86_64}/lib/ . Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'arch/i386')
-rw-r--r--arch/i386/lib/Makefile2
-rw-r--r--arch/i386/lib/msr-on-cpu.c70
2 files changed, 72 insertions, 0 deletions
diff --git a/arch/i386/lib/Makefile b/arch/i386/lib/Makefile
index d86a548b8d5..0d41223472c 100644
--- a/arch/i386/lib/Makefile
+++ b/arch/i386/lib/Makefile
@@ -7,3 +7,5 @@ lib-y = checksum.o delay.o usercopy.o getuser.o putuser.o memcpy.o strstr.o \
bitops.o semaphore.o
lib-$(CONFIG_X86_USE_3DNOW) += mmx.o
+
+obj-y = msr-on-cpu.o
diff --git a/arch/i386/lib/msr-on-cpu.c b/arch/i386/lib/msr-on-cpu.c
new file mode 100644
index 00000000000..2092ea15ba8
--- /dev/null
+++ b/arch/i386/lib/msr-on-cpu.c
@@ -0,0 +1,70 @@
+#include <linux/module.h>
+#include <linux/preempt.h>
+#include <linux/smp.h>
+#include <asm/msr.h>
+
+#ifdef CONFIG_SMP
+struct msr_info {
+ u32 msr_no;
+ u32 l, h;
+};
+
+static void __rdmsr_on_cpu(void *info)
+{
+ struct msr_info *rv = info;
+
+ rdmsr(rv->msr_no, rv->l, rv->h);
+}
+
+void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+ preempt_disable();
+ if (smp_processor_id() == cpu)
+ rdmsr(msr_no, *l, *h);
+ else {
+ struct msr_info rv;
+
+ rv.msr_no = msr_no;
+ smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 0, 1);
+ *l = rv.l;
+ *h = rv.h;
+ }
+ preempt_enable();
+}
+
+static void __wrmsr_on_cpu(void *info)
+{
+ struct msr_info *rv = info;
+
+ wrmsr(rv->msr_no, rv->l, rv->h);
+}
+
+void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+ preempt_disable();
+ if (smp_processor_id() == cpu)
+ wrmsr(msr_no, l, h);
+ else {
+ struct msr_info rv;
+
+ rv.msr_no = msr_no;
+ rv.l = l;
+ rv.h = h;
+ smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 0, 1);
+ }
+ preempt_enable();
+}
+#else
+void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+ rdmsr(msr_no, *l, *h);
+}
+
+void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+ wrmsr(msr_no, l, h);
+}
+#endif
+
+EXPORT_SYMBOL(rdmsr_on_cpu);
+EXPORT_SYMBOL(wrmsr_on_cpu);