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SubjectRe: [PATCH] tsc-disable_B9
From
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On Thu, 2002-08-08 at 02:53, john stultz wrote:
> already seen on another cpu. This patch allows people compiling w/
> 'Multi-node NUMA support' to pass "notsc" or "bad-tsc" as boot
> parameters. "notsc" disables rdtsc calls, and forces the kernel to use
> the PIT for gettimeofday calucluations (as normally expected w/ i386
> compiled kernels). While "bad-tsc" forces the kernel to use the PIT for
> gettimeofday, but does not disable TSC access.

I've done a version of this for -ac which uses the NUMA autodetect, and
also provides the hook so I can disable tsc on split on x86 smp with
variable multipliers some time. The only comment I really have is please
use "badtsc" not "bad-tsc" - to match "notsc"

This is how I did it - barring the code that is -ac specific to automatically flip
the mode when NUMA hw is detected


diff -u --exclude-from /usr/src/exclude --new-file --recursive linux.20pre1/include/asm-i386/processor.h linux.20pre1-ac2/include/asm-i386/processor.h
--- linux.20pre1/include/asm-i386/processor.h 2002-08-06 15:40:34.000000000 +0100
+++ linux.20pre1-ac2/include/asm-i386/processor.h 2002-08-07 15:23:39.000000000 +0100
@@ -96,7 +96,7 @@

extern void identify_cpu(struct cpuinfo_x86 *);
extern void print_cpu_info(struct cpuinfo_x86 *);
-extern void dodgy_tsc(void);
+extern int dodgy_tsc(void);

/*
* EFLAGS bits
--- linux.vanilla/arch/i386/kernel/time.c 2002-02-25 19:37:53.000000000 +0000
+++ linux.20pre1-ac2/arch/i386/kernel/time.c 2002-08-08 12:56:48.000000000 +0100
@@ -666,9 +666,7 @@
* moaned if you have the only one in the world - you fix it!
*/

- dodgy_tsc();
-
- if (cpu_has_tsc) {
+ if (!dodgy_tsc()) {
unsigned long tsc_quotient = calibrate_tsc();
if (tsc_quotient) {
fast_gettimeoffset_quotient = tsc_quotient;
diff -u --exclude-from /usr/src/exclude --new-file --recursive linux.20pre1/arch/i386/kernel/setup.c linux.20pre1-ac2/arch/i386/kernel/setup.c
--- linux.20pre1/arch/i386/kernel/setup.c 2002-08-06 15:41:42.000000000 +0100
+++ linux.20pre1-ac2/arch/i386/kernel/setup.c 2002-08-07 15:23:29.000000000 +0100
@@ -1193,19 +1126,51 @@
}
__setup("cachesize=", cachesize_setup);

-
#ifndef CONFIG_X86_TSC
+
static int tsc_disable __initdata = 0;

-static int __init tsc_setup(char *str)
+void disable_tsc(void)
+{
+ if(tsc_disable == 0)
+ {
+ printk(KERN_INFO "Disabling use of TSC for time counting.\n");
+ tsc_disable = 1;
+ }
+}
+
+/* Disable TSC on processor and also for get time of day */
+
+static int __init notsc_setup(char *str)
+{
+ tsc_disable = 2;
+ return 1;
+}
+
+__setup("notsc", notsc_setup);
+
+/* Allow TSC use but don't use it for gettimeofday */
+
+static int __init badtsc_setup(char *str)
{
tsc_disable = 1;
return 1;
}

-__setup("notsc", tsc_setup);
+__setup("badtsc", badtsc_setup);
+
+#else
+
+#define tsc_disable 0
+
+void disable_tsc(void)
+{
+ panic("Time stamp counter required by this kernel, but not supported by the hardware.\n");
+}
+
#endif

+
static int __init get_model_name(struct cpuinfo_x86 *c)
{
unsigned int *v;
@@ -2843,10 +2762,8 @@
*/

/* TSC disabled? */
-#ifndef CONFIG_X86_TSC
- if ( tsc_disable )
+ if ( tsc_disable > 1 )
clear_bit(X86_FEATURE_TSC, &c->x86_capability);
-#endif

/* HT disabled? */
if (disable_x86_ht)
@@ -2906,13 +2823,23 @@
* Perform early boot up checks for a valid TSC. See arch/i386/kernel/time.c
*/

-void __init dodgy_tsc(void)
+int __init dodgy_tsc(void)
{
get_cpu_vendor(&boot_cpu_data);

if ( boot_cpu_data.x86_vendor == X86_VENDOR_CYRIX ||
boot_cpu_data.x86_vendor == X86_VENDOR_NSC )
init_cyrix(&boot_cpu_data);
+
+ /* Is it disabled ? */
+ if(tsc_disable)
+ return 1;
+
+ /* Does it exist ? */
+ if(!cpu_has_tsc)
+ return 1;
+
+ return 0;
}


@@ -3088,14 +3021,12 @@

if (cpu_has_vme || cpu_has_tsc || cpu_has_de)
clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
-#ifndef CONFIG_X86_TSC
- if (tsc_disable && cpu_has_tsc) {
+ if (tsc_disable > 1 && cpu_has_tsc) {
printk(KERN_NOTICE "Disabling TSC...\n");
/**** FIX-HPA: DOES THIS REALLY BELONG HERE? ****/
clear_bit(X86_FEATURE_TSC, boot_cpu_data.x86_capability);
set_in_cr4(X86_CR4_TSD);
}
-#endif

__asm__ __volatile__("lgdt %0": "=m" (gdt_descr));
__asm__ __volatile__("lidt %0": "=m" (idt_descr));
-
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