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[PATCH] paravirt: Add option to allow skipping the timer check

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Add a way to disable the timer IRQ routing check via a boot option.  The
VMI timer code uses this to avoid triggering the pester Mingo code, which
probes for some very unusual and broken motherboard routings.  It fires
100% of the time when using a paravirtual delay mechanism instead of using
a realtime delay, since there is no elapsed real time, and the 4 timer IRQs
have not yet been delivered.

In addition, it is entirely possible, though improbable, that this bug
could surface on real hardware which picks a particularly bad time to enter
SMM mode, causing a long latency during one of the timer IRQs.

While here, make check_timer be __init.

Signed-off-by: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andi Kleen <ak@suse.de>
[chrisw: use no_timer_check to bring inline with x86_64 as per Andi's request]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
This commit is contained in:
Zachary Amsden
2006-12-07 02:14:09 +01:00
committed by Andi Kleen
parent 8ecb895069
commit 8542b200cb
2 changed files with 19 additions and 4 deletions
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16
arch/i386/kernel/io_apic.c
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@@ -1932,6 +1932,15 @@ static void __init setup_ioapic_ids_from_mpc(void)
static void __init setup_ioapic_ids_from_mpc(void) { }
#endif
static int no_timer_check __initdata;
static int __init notimercheck(char *s)
{
no_timer_check = 1;
return 1;
}
__setup("no_timer_check", notimercheck);
/*
* There is a nasty bug in some older SMP boards, their mptable lies
* about the timer IRQ. We do the following to work around the situation:
@@ -1940,10 +1949,13 @@ static void __init setup_ioapic_ids_from_mpc(void) { }
* - if this function detects that timer IRQs are defunct, then we fall
* back to ISA timer IRQs
*/
static int __init timer_irq_works(void)
int __init timer_irq_works(void)
{
unsigned long t1 = jiffies;
if (no_timer_check)
return 1;
local_irq_enable();
/* Let ten ticks pass... */
mdelay((10 * 1000) / HZ);
@@ -2214,7 +2226,7 @@ int timer_uses_ioapic_pin_0;
* is so screwy. Thanks to Brian Perkins for testing/hacking this beast
* fanatically on his truly buggy board.
*/
static inline void check_timer(void)
static inline void __init check_timer(void)
{
int apic1, pin1, apic2, pin2;
int vector;