i386: Add safe variants of rdmsr_on_cpu and wrmsr_on_cpu

Add safe (exception handled) variants of rdmsr_on_cpu and wrmsr_on_cpu.
You should use these when the target MSR may not actually exist, as
doing so could trigger an exception which the regular functions do not
handle. The safe variants are slower, though.

The upcoming coretemp hardware monitoring driver will need this.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Cc: Alexey Dobriyan <adobriyan@openvz.org>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 67 insertions, 6 deletions

diff --git a/arch/i386/lib/msr-on-cpu.c b/arch/i386/lib/msr-on-cpu.c
index 1c46bda409f..7767962f25d 100644
--- a/arch/i386/lib/msr-on-cpu.c
+++ b/arch/i386/lib/msr-on-cpu.c
@@ -6,6 +6,7 @@
 struct msr_info {
 	u32 msr_no;
 	u32 l, h;
+	int err;
 };
 
 static void __rdmsr_on_cpu(void *info)
@@ -15,20 +16,38 @@ static void __rdmsr_on_cpu(void *info)
 	rdmsr(rv->msr_no, rv->l, rv->h);
 }
 
-void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+static void __rdmsr_safe_on_cpu(void *info)
 {
+	struct msr_info *rv = info;
+
+	rv->err = rdmsr_safe(rv->msr_no, &rv->l, &rv->h);
+}
+
+static int _rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h, int safe)
+{
+	int err = 0;
 	preempt_disable();
 	if (smp_processor_id() == cpu)
-		rdmsr(msr_no, *l, *h);
+		if (safe)
+			err = rdmsr_safe(msr_no, l, h);
+		else
+			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);
+		if (safe) {
+			smp_call_function_single(cpu, __rdmsr_safe_on_cpu,
+						 &rv, 0, 1);
+			err = rv.err;
+		} else {
+			smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 0, 1);
+		}
 		*l = rv.l;
 		*h = rv.h;
 	}
 	preempt_enable();
+	return err;
 }
 
 static void __wrmsr_on_cpu(void *info)
@@ -38,21 +57,63 @@ static void __wrmsr_on_cpu(void *info)
 	wrmsr(rv->msr_no, rv->l, rv->h);
 }
 
-void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+static void __wrmsr_safe_on_cpu(void *info)
 {
+	struct msr_info *rv = info;
+
+	rv->err = wrmsr_safe(rv->msr_no, rv->l, rv->h);
+}
+
+static int _wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h, int safe)
+{
+	int err = 0;
 	preempt_disable();
 	if (smp_processor_id() == cpu)
-		wrmsr(msr_no, l, h);
+		if (safe)
+			err = wrmsr_safe(msr_no, l, h);
+		else
+			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);
+		if (safe) {
+			smp_call_function_single(cpu, __wrmsr_safe_on_cpu,
+						 &rv, 0, 1);
+			err = rv.err;
+		} else {
+			smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 0, 1);
+		}
 	}
 	preempt_enable();
+	return err;
+}
+
+void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+	_wrmsr_on_cpu(cpu, msr_no, l, h, 0);
+}
+
+void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+	_rdmsr_on_cpu(cpu, msr_no, l, h, 0);
+}
+
+/* These "safe" variants are slower and should be used when the target MSR
+   may not actually exist. */
+int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+	return _wrmsr_on_cpu(cpu, msr_no, l, h, 1);
+}
+
+int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+	return _rdmsr_on_cpu(cpu, msr_no, l, h, 1);
 }
 
 EXPORT_SYMBOL(rdmsr_on_cpu);
 EXPORT_SYMBOL(wrmsr_on_cpu);
+EXPORT_SYMBOL(rdmsr_safe_on_cpu);
+EXPORT_SYMBOL(wrmsr_safe_on_cpu);