linux-kernel - Re: [PATCH] x86: APIC: Remove apic_write

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Date:	Fri, 18 Jul 2008 09:25:55 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Maciej W. Rozycki" <macro@...ux-mips.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	"Suresh Siddha" <suresh.b.siddha@...el.com>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>
Subject: Re: [PATCH] x86: APIC: Remove apic_write_around(); use alternatives

On Fri, Jul 18, 2008 at 3:52 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Maciej W. Rozycki <macro@...ux-mips.org> wrote:
>
>>  Use alternatives to select the workaround for the 11AP Pentium
>> erratum for the affected steppings on the fly rather than build time.
>> Remove the X86_GOOD_APIC configuration option and replace all the
>> calls to apic_write_around() with plain apic_write(), protecting
>> accesses to the ESR as appropriate due to the 3AP Pentium erratum.
>> Remove apic_read_around() and all its invocations altogether as not
>> needed.  Remove apic_write_atomic() and all its implementing backends.
>> The use of ASM_OUTPUT2() is not strictly needed for input constraints,
>> but I have used it for readability's sake.
>
> wow, impressive patch!
>
>>  I had the feeling no one else was brave enough to do it, so I went
>> ahead and here it is.  Verified by checking the generated assembly and
>> tested with both a 32-bit and a 64-bit configuration, also with the
>> 11AP "feature" forced on and verified with gdb on /proc/kcore to work
>> as expected (as an 11AP machines are quite hard to get hands on these
>> days).  Some script complained about the use of "volatile", but
>> apic_write() needs it for the same reason and is effectively a
>> replacement for writel(), so I have disregarded it.
>
> kudos for pulling this off :-)
>
> applied to tip/x86/apic. This will interact with tip/x86/x2apic but that
> topic is being worked on anyway. The interaction should be trivial.

it seems we should start apic related merging after x2apic get merged?

YH
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