Name: Neater returns for i386/x86_64 cpuid/msr on Offline CPUs
Status: Untested
Depends: 
Depends: Misc/on_one_cpu.patch.gz

You can open an MSR or CPUID file on a cpu, and then it can go down.
You'll get junk/noop; nicer to return an error on read/write in this
case.

Use on_one_cpu() as well.  It's just easier to read.

diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8202-linux-2.6.6-bk6/arch/i386/kernel/cpuid.c .8202-linux-2.6.6-bk6.updated/arch/i386/kernel/cpuid.c
--- .8202-linux-2.6.6-bk6/arch/i386/kernel/cpuid.c	2004-05-20 19:40:03.000000000 +1000
+++ .8202-linux-2.6.6-bk6.updated/arch/i386/kernel/cpuid.c	2004-05-20 19:52:36.000000000 +1000
@@ -42,48 +42,33 @@
 #include <asm/uaccess.h>
 #include <asm/system.h>
 
-#ifdef CONFIG_SMP
-
 struct cpuid_command {
-	int cpu;
+	int err;
 	u32 reg;
 	u32 *data;
 };
 
-static void cpuid_smp_cpuid(void *cmd_block)
+static inline void __do_cpuid(void *cmd_block)
 {
 	struct cpuid_command *cmd = (struct cpuid_command *)cmd_block;
 
-	if (cmd->cpu == smp_processor_id())
-		cpuid(cmd->reg, &cmd->data[0], &cmd->data[1], &cmd->data[2],
-		      &cmd->data[3]);
+	cpuid(cmd->reg, &cmd->data[0], &cmd->data[1], &cmd->data[2],
+	      &cmd->data[3]);
+	cmd->err = 0;
 }
 
-static inline void do_cpuid(int cpu, u32 reg, u32 * data)
+static inline int do_cpuid(int cpu, u32 reg, u32 * data)
 {
 	struct cpuid_command cmd;
 
-	preempt_disable();
-	if (cpu == smp_processor_id()) {
-		cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
-	} else {
-		cmd.cpu = cpu;
-		cmd.reg = reg;
-		cmd.data = data;
-
-		smp_call_function(cpuid_smp_cpuid, &cmd, 1, 1);
-	}
-	preempt_enable();
-}
-#else				/* ! CONFIG_SMP */
+	cmd.reg = reg;
+	cmd.data = data;
+	cmd.err = -ENOENT;
 
-static inline void do_cpuid(int cpu, u32 reg, u32 * data)
-{
-	cpuid(reg, &data[0], &data[1], &data[2], &data[3]);
+	on_one_cpu(cpu, __do_cpuid, &cmd);
+	return cmd.err;
 }
 
-#endif				/* ! CONFIG_SMP */
-
 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
 {
 	loff_t ret;
@@ -114,13 +99,15 @@ static ssize_t cpuid_read(struct file *f
 	u32 data[4];
 	size_t rv;
 	u32 reg = *ppos;
-	int cpu = iminor(file->f_dentry->d_inode);
+	int err, cpu = iminor(file->f_dentry->d_inode);
 
 	if (count % 16)
 		return -EINVAL;	/* Invalid chunk size */
 
 	for (rv = 0; count; count -= 16) {
-		do_cpuid(cpu, reg, data);
+		err = do_cpuid(cpu, reg, data);
+		if (err)
+			return err;
 		if (copy_to_user(tmp, &data, 16))
 			return -EFAULT;
 		tmp += 4;
diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal .8202-linux-2.6.6-bk6/arch/i386/kernel/msr.c .8202-linux-2.6.6-bk6.updated/arch/i386/kernel/msr.c
--- .8202-linux-2.6.6-bk6/arch/i386/kernel/msr.c	2004-05-20 19:40:03.000000000 +1000
+++ .8202-linux-2.6.6-bk6.updated/arch/i386/kernel/msr.c	2004-05-20 19:52:49.000000000 +1000
@@ -86,89 +86,53 @@ static inline int rdmsr_eio(u32 reg, u32
   return err;
 }
 
-#ifdef CONFIG_SMP
-
 struct msr_command {
-  int cpu;
   int err;
   u32 reg;
   u32 data[2];
 };
 
-static void msr_smp_wrmsr(void *cmd_block)
+static inline void __msr_wrmsr(void *cmd_block)
 {
   struct msr_command *cmd = (struct msr_command *) cmd_block;
   
-  if ( cmd->cpu == smp_processor_id() )
-    cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
+  cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
 }
 
-static void msr_smp_rdmsr(void *cmd_block)
+static inline void __msr_rdmsr(void *cmd_block)
 {
   struct msr_command *cmd = (struct msr_command *) cmd_block;
   
-  if ( cmd->cpu == smp_processor_id() )
-    cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
+  cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
 }
 
 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 {
   struct msr_command cmd;
-  int ret;
 
-  preempt_disable();
-  if ( cpu == smp_processor_id() ) {
-    ret = wrmsr_eio(reg, eax, edx);
-  } else {
-    cmd.cpu = cpu;
-    cmd.reg = reg;
-    cmd.data[0] = eax;
-    cmd.data[1] = edx;
-    
-    smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
-    ret = cmd.err;
-  }
-  preempt_enable();
-  return ret;
+  cmd.reg = reg;
+  cmd.data[0] = eax;
+  cmd.data[1] = edx;
+  cmd.err = -ENOENT;
+
+  on_one_cpu(cpu, __msr_wrmsr, &cmd);
+  return cmd.err;
 }
 
 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
 {
   struct msr_command cmd;
-  int ret;
-
-  preempt_disable();
-  if ( cpu == smp_processor_id() ) {
-    ret = rdmsr_eio(reg, eax, edx);
-  } else {
-    cmd.cpu = cpu;
-    cmd.reg = reg;
-
-    smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
-    
-    *eax = cmd.data[0];
-    *edx = cmd.data[1];
 
-    ret = cmd.err;
-  }
-  preempt_enable();
-  return ret;
-}
-
-#else /* ! CONFIG_SMP */
+  cmd.reg = reg;
+  cmd.err = -ENOENT;
 
-static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
-{
-  return wrmsr_eio(reg, eax, edx);
-}
+  on_one_cpu(cpu, __msr_rdmsr, &cmd);
 
-static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
-{
-  return rdmsr_eio(reg, eax, edx);
+  *eax = cmd.data[0];
+  *edx = cmd.data[1];
+  return cmd.err;
 }
 
-#endif /* ! CONFIG_SMP */
-
 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 {
   loff_t ret = -EINVAL;