x86: msr: propagate errors from smp_call_function_single()

Propagate error (-ENXIO) from smp_call_function_single().  These
errors can happen when a CPU is unplugged while the MSR driver is
open.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 22 insertions, 14 deletions

diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index e43938086885..9c34a1005dba 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -79,8 +79,11 @@ static ssize_t msr_read(struct file *file, char __user *buf,
 
         for (; count; count -= 8) {
                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
-                if (err)
-                        return -EIO;
+                if (err) {
+                        if (err == -EFAULT) /* Fix idiotic error code */
+                                err = -EIO;
+                        return err;
+                }
                 if (copy_to_user(tmp, &data, 8))
                         return -EFAULT;
                 tmp += 2;
@@ -105,8 +108,11 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
                 if (copy_from_user(&data, tmp, 8))
                         return -EFAULT;
                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
-                if (err)
-                        return -EIO;
+                if (err) {
+                        if (err == -EFAULT) /* Fix idiotic error code */
+                                err = -EIO;
+                        return err;
+                }
                 tmp += 2;
         }
 
diff --git a/arch/x86/lib/msr-on-cpu.c b/arch/x86/lib/msr-on-cpu.c
index d5a2b39f882b..01b868ba82f8 100644
--- a/arch/x86/lib/msr-on-cpu.c
+++ b/arch/x86/lib/msr-on-cpu.c
@@ -30,10 +30,11 @@ static int _rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h, int safe)
 
         rv.msr_no = msr_no;
         if (safe) {
-                smp_call_function_single(cpu, __rdmsr_safe_on_cpu, &rv, 1);
-                err = rv.err;
+                err = smp_call_function_single(cpu, __rdmsr_safe_on_cpu,
+                                               &rv, 1);
+                err = err ? err : rv.err;
         } else {
-                smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 1);
+                err = smp_call_function_single(cpu, __rdmsr_on_cpu, &rv, 1);
         }
         *l = rv.l;
         *h = rv.h;
@@ -64,23 +65,24 @@ static int _wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h, int safe)
         rv.l = l;
         rv.h = h;
         if (safe) {
-                smp_call_function_single(cpu, __wrmsr_safe_on_cpu, &rv, 1);
-                err = rv.err;
+                err = smp_call_function_single(cpu, __wrmsr_safe_on_cpu,
+                                               &rv, 1);
+                err = err ? err : rv.err;
         } else {
-                smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 1);
+                err = smp_call_function_single(cpu, __wrmsr_on_cpu, &rv, 1);
         }
 
         return err;
 }
 
-void wrmsr_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)
 {
-        _wrmsr_on_cpu(cpu, msr_no, l, h, 0);
+        return _wrmsr_on_cpu(cpu, msr_no, l, h, 0);
 }
 
-void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
+int rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h)
 {
-        _rdmsr_on_cpu(cpu, msr_no, l, h, 0);
+        return _rdmsr_on_cpu(cpu, msr_no, l, h, 0);
 }
 
 /* These "safe" variants are slower and should be used when the target MSR