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x86: apic - introduce dummy apic operations

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Impact: refactor, speed up and robustize code

In case if apic was disabled by kernel option
or by hardware limits we can use dummy operations
in apic->write to simplify the ack_APIC_irq() code.

At the lame time the patch fixes the missed EOI in
do_IRQ function (which has place if kernel is compiled
as X86-32 and interrupt without handler happens where
apic was not asked to be disabled via kernel option).

Note that native_apic_write_dummy() consists of
WARN_ON_ONCE to catch any buggy writes on enabled
APICs. Could be removed after some time of testing.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
LKML-Reference: <20090412165058.724788431@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Cyrill Gorcunov 2009-04-12 20:47:41 +04:00 • committed by Ingo Molnar
parent c0eaa4536f
commit 08306ce61d
3 changed files with 28 additions and 9 deletions
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24
arch/x86/kernel/apic/apic.c
View file

@ -232,6 +232,24 @@ static int modern_apic(void)
return lapic_get_version() >= 0x14;
}
/*
* bare function to substitute write operation
* and it's _that_ fast :)
*/
void native_apic_write_dummy(u32 reg, u32 v)
{
WARN_ON_ONCE((cpu_has_apic || !disable_apic));
}
/*
* right after this call apic->write doesn't do anything
* note that there is no restore operation it works one way
*/
void apic_disable(void)
{
apic->write = native_apic_write_dummy;
}
void native_apic_wait_icr_idle(void)
{
while (apic_read(APIC_ICR) & APIC_ICR_BUSY)
@ -1582,6 +1600,12 @@ void __init init_apic_mappings(void)
*/
if (boot_cpu_physical_apicid == -1U)
boot_cpu_physical_apicid = read_apic_id();
/* lets check if we may to NOP'ify apic operations */
if (!cpu_has_apic) {
pr_info("APIC: disable apic facility\n");
apic_disable();
}
}
/*