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>

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);

include/asm-i386/msr.h

@@ -77,7 +77,7 @@ static inline unsigned long long native_read_pmc(void)
 #ifdef CONFIG_PARAVIRT
 #include <asm/paravirt.h>
 #else
-
+#include <linux/errno.h>
 /*
  * Access to machine-specific registers (available on 586 and better only)
  * Note: the rd* operations modify the parameters directly (without using
@@ -148,6 +148,8 @@ static inline void wrmsrl (unsigned long msr, unsigned long long val)
 #ifdef CONFIG_SMP
 void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
 void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
+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  */
 static inline void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 {
@@ -157,6 +159,14 @@ static inline void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
 {
 	wrmsr(msr_no, l, h);
 }
+static inline int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+	return rdmsr_safe(msr_no, l, h);
+}
+static inline int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+	return wrmsr_safe(msr_no, l, h);
+}
 #endif  /*  CONFIG_SMP  */
 #endif
 #endif

include/asm-x86_64/msr.h

@@ -4,6 +4,7 @@
 #include <asm/msr-index.h>
 
 #ifndef __ASSEMBLY__
+#include <linux/errno.h>
 /*
  * Access to machine-specific registers (available on 586 and better only)
  * Note: the rd* operations modify the parameters directly (without using
@@ -162,6 +163,8 @@ static inline unsigned int cpuid_edx(unsigned int op)
 #ifdef CONFIG_SMP
 void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);
 void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);
+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  */
 static inline void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 {
@@ -171,6 +174,14 @@ static inline void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
 {
 	wrmsr(msr_no, l, h);
 }
+static inline int rdmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+{
+	return rdmsr_safe(msr_no, l, h);
+}
+static inline int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
+{
+	return wrmsr_safe(msr_no, l, h);
+}
 #endif  /* CONFIG_SMP */
 #endif /* __ASSEMBLY__ */
 #endif	/* X86_64_MSR_H */