linux-kernel - Re: [PATCH 1/3] x86: add lapic_shutdown for x86

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Date:	Wed, 24 Oct 2007 14:27:46 -0700
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	vgoyal@...ibm.com
Cc:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>, hbabu@...ibm.com,
	tglx@...utronix.de, linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 1/3] x86: add lapic_shutdown for x86_64

Vivek Goyal wrote:
> On Fri, Oct 19, 2007 at 06:21:11PM -0700, Hiroshi Shimamoto wrote:
>> From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
>>
>> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
>> ---
>>  arch/x86/kernel/apic_64.c |   14 ++++++++++++++
>>  include/asm-x86/apic_64.h |    1 +
>>  2 files changed, 15 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
>> index f47bc49..f28ccb5 100644
>> --- a/arch/x86/kernel/apic_64.c
>> +++ b/arch/x86/kernel/apic_64.c
>> @@ -287,6 +287,20 @@ void disable_local_APIC(void)
>>  	apic_write(APIC_SPIV, value);
>>  }
>>
>> +void lapic_shutdown(void)
>> +{
>> +	unsigned long flags;
>> +
>> +	if (!cpu_has_apic)
>> +		return;
>> +
>> +	local_irq_save(flags);
>> +
>> +	disable_local_APIC();
>> +
>> +	local_irq_restore(flags);
>> +}
>> +
>>  /*
> 
> Do we really have to introduce this function for 64bit? I remember some
> issues were faced on i386 w.r.t kernel enabling the LAPIC against the
> wishes of BIOS hence kernel was disabling it while shutting down. No
> such problems were reported for x86_64 hence this function existed only
> for i386.

Thanks for the comment. I didn't know the issues, so I'd simply added
this function for unification.

> If that is the case, probably we don't have to introduce lapic_shutdown()
> for x86_64. Instead call lapic_shutdown() for X86_32, and disble_local_APIC()
> otherwise?

I will do that. I was thinking which is good when posting these patches.

Thanks
Hiroshi Shimamoto
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