/proc/mtrr in 2.6

/proc/mtrr in 2.6

[kernel]

In 2.6, having /proc/mtrr support in a kernel run on a system which
lacks MTRR support (like my crusoe) results in /proc/mtrr existing, but
giving EIO if you try to read it. On 2.4, it is detected as not existing
and not created. Is this the new intentional behaviour, or just a bug?

Re: /proc/mtrr in 2.6

[Dave Jones]

On Tue, Nov 18, 2003 at 09:12:34PM -0800, kernel@mikebell.org wrote:
 > In 2.6, having /proc/mtrr support in a kernel run on a system which
 > lacks MTRR support (like my crusoe) results in /proc/mtrr existing, but
 > giving EIO if you try to read it. On 2.4, it is detected as not existing
 > and not created. Is this the new intentional behaviour, or just a bug?

Need something like this perhaps ?

--- 1/arch/i386/kernel/cpu/mtrr/if.c~	2003-11-19 16:00:10.000000000 +0000
+++ 2/arch/i386/kernel/cpu/mtrr/if.c	2003-11-19 16:09:25.000000000 +0000
@@ -352,6 +352,14 @@
 
 static int __init mtrr_if_init(void)
 {
+	struct cpuinfo_x86 *c = &boot_cpu_data;
+
+	if ((!cpu_has(c, X86_FEATURE_MTRR)) ||
+	    (!cpu_has(c, X86_FEATURE_K6_MTRR)) ||
+	    (!cpu_has(c, X86_FEATURE_CYRIX_ARR)) ||
+	    (!cpu_has(c, X86_FEATURE_CENTAUR_MCR)))
+		return -ENODEV;
+
 	proc_root_mtrr =
 	    create_proc_entry("mtrr", S_IWUSR | S_IRUGO, &proc_root);
 	if (proc_root_mtrr) {

Re: /proc/mtrr in 2.6

[Dave Jones]

On Wed, Nov 19, 2003 at 04:10:44PM +0000, Dave Jones wrote:
 > On Tue, Nov 18, 2003 at 09:12:34PM -0800, kernel@mikebell.org wrote:
 >  > In 2.6, having /proc/mtrr support in a kernel run on a system which
 >  > lacks MTRR support (like my crusoe) results in /proc/mtrr existing, but
 >  > giving EIO if you try to read it. On 2.4, it is detected as not existing
 >  > and not created. Is this the new intentional behaviour, or just a bug?
 > 
 > Need something like this perhaps ?

Better yet, get the logic right..


--- linux-2.5/arch/i386/kernel/cpu/mtrr/if.c~	Wed Nov 19 17:04:50 2003
+++ linux-2.5/arch/i386/kernel/cpu/mtrr/if.c	Wed Nov 19 17:05:29 2003
@@ -352,6 +352,14 @@
 
 static int __init mtrr_if_init(void)
 {
+	struct cpuinfo_x86 *c = &boot_cpu_data;
+
+	if ((!cpu_has(c, X86_FEATURE_MTRR)) &&
+		(!cpu_has(c, X86_FEATURE_K6_MTRR)) &&
+		(!cpu_has(c, X86_FEATURE_CYRIX_ARR)) &&
+		(!cpu_has(c, X86_FEATURE_CENTAUR_MCR)))
+	return -ENODEV;
+
 	proc_root_mtrr =
 	    create_proc_entry("mtrr", S_IWUSR | S_IRUGO, &proc_root);
 	if (proc_root_mtrr) {