x86: cpuid: allow querying %ecx-sensitive CPUID levels

After /dev/*/cpuid was introduced, Intel changed the semantics of the
CPUID instruction to be sentitive to %ecx as well as %eax.  This patch
allows querying of %ecx-sensitive levels by placing the %ecx value in
the upper 32 bits of the file position (lower 32 bits always were used
for the %eax value.)

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 20 insertions, 25 deletions

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index a63432d800f9..c10ebc4b8e4b 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
- *   
- *   Copyright 2000 H. Peter Anvin - All Rights Reserved
+ *
+ *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -17,6 +17,10 @@
  * and then read in chunks of 16 bytes.  A larger size means multiple
  * reads of consecutive levels.
  *
+ * The lower 32 bits of the file position is used as the incoming %eax,
+ * and the upper 32 bits of the file position as the incoming %ecx,
+ * the latter intended for "counting" eax levels like eax=4.
+ *
  * This driver uses /dev/cpu/%d/cpuid where %d is the minor number, and on
  * an SMP box will direct the access to CPU %d.
  */
@@ -43,27 +47,16 @@
 
 static struct class *cpuid_class;
 
-struct cpuid_command {
-        u32 reg;
-        u32 *data;
+struct cpuid_regs {
+        u32 eax, ebx, ecx, edx;
 };
 
 static void cpuid_smp_cpuid(void *cmd_block)
 {
-        struct cpuid_command *cmd = cmd_block;
-
-        cpuid(cmd->reg, &cmd->data[0], &cmd->data[1], &cmd->data[2],
-                      &cmd->data[3]);
-}
-
-static inline void do_cpuid(int cpu, u32 reg, u32 * data)
-{
-        struct cpuid_command cmd;
+        struct cpuid_regs *cmd = (struct cpuid_regs *)cmd_block;
 
-        cmd.reg = reg;
-        cmd.data = data;
-
-        smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
+        cpuid_count(cmd->eax, cmd->ecx,
+                    &cmd->eax, &cmd->ebx, &cmd->ecx, &cmd->edx);
 }
 
 static loff_t cpuid_seek(struct file *file, loff_t offset, int orig)
@@ -93,19 +86,21 @@ static ssize_t cpuid_read(struct file *file, char __user *buf,
                           size_t count, loff_t * ppos)
 {
         char __user *tmp = buf;
-        u32 data[4];
-        u32 reg = *ppos;
+        struct cpuid_regs cmd;
         int cpu = iminor(file->f_path.dentry->d_inode);
+        u64 pos = *ppos;
 
         if (count % 16)
                 return -EINVAL; /* Invalid chunk size */
 
         for (; count; count -= 16) {
-                do_cpuid(cpu, reg, data);
-                if (copy_to_user(tmp, &data, 16))
+                cmd.eax = pos;
+                cmd.ecx = pos >> 32;
+                smp_call_function_single(cpu, cpuid_smp_cpuid, &cmd, 1, 1);
+                if (copy_to_user(tmp, &cmd, 16))
                         return -EFAULT;
                 tmp += 16;
-                *ppos = reg++;
+                *ppos = ++pos;
         }
 
         return tmp - buf;
@@ -193,7 +188,7 @@ static int __init cpuid_init(void)
         }
         for_each_online_cpu(i) {
                 err = cpuid_device_create(i);
-                if (err != 0) 
+                if (err != 0)
                         goto out_class;
         }
         register_hotcpu_notifier(&cpuid_class_cpu_notifier);
@@ -208,7 +203,7 @@ out_class:
         }
         class_destroy(cpuid_class);
 out_chrdev:
-        unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");    
+        unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
 out:
         return err;
 }