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x86/smpboot: Fix cpu_init_udelay=10000 corner case boot parameter misbehavior

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For legacy machines cpu_init_udelay defaults to 10,000.
For modern machines it is set to 0.

The user should be able to set cpu_init_udelay to
any value on the cmdline, including 10,000.

Before this patch, that was seen as "unchanged from default"
and thus on a modern machine, the user request was ignored
and the delay was set to 0.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dparsons@brightdsl.net
Cc: shrybman@teksavvy.com
Link: http://lkml.kernel.org/r/de363cdbbcfcca1d22569683f7eb9873e0177251.1444968087.git.len.brown@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Len Brown 2015-10-16 00:14:28 -04:00 committed by Ingo Molnar
parent c0ff971ef9
commit f1ccd24931
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kernel/smpboot.c
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@ -509,7 +509,7 @@ void __inquire_remote_apic(int apicid)
*/
#define UDELAY_10MS_DEFAULT 10000
static unsigned int init_udelay = UDELAY_10MS_DEFAULT;
static unsigned int init_udelay = INT_MAX;
static int __init cpu_init_udelay(char *str)
{
@ -522,13 +522,16 @@ early_param("cpu_init_udelay", cpu_init_udelay);
static void __init smp_quirk_init_udelay(void)
{
/* if cmdline changed it from default, leave it alone */
if (init_udelay != UDELAY_10MS_DEFAULT)
if (init_udelay != INT_MAX)
return;
/* if modern processor, use no delay */
if (((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 == 6)) ||
((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && (boot_cpu_data.x86 >= 0xF)))
init_udelay = 0;
/* else, use legacy delay */
init_udelay = UDELAY_10MS_DEFAULT;
}
/*