linux-kernel - RE: unnecessary #ifdefs

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Date:	Wed, 27 May 2015 00:17:29 +0000
From:	"Wu, Feng" <feng.wu@...el.com>
To:	Stefan Hengelein <stefan.hengelein@....de>
CC:	Valentin Rothberg <valentinrothberg@...il.com>,
	Paul Bolle <pebolle@...cali.nl>,
	Andreas Ruprecht <rupran@...server.de>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Wu, Feng" <feng.wu@...el.com>
Subject: RE: unnecessary #ifdefs



> -----Original Message-----
> From: ilendir@...il.com [mailto:ilendir@...il.com] On Behalf Of Stefan
> Hengelein
> Sent: Wednesday, May 27, 2015 2:19 AM
> To: Wu, Feng
> Cc: Valentin Rothberg; Paul Bolle; Andreas Ruprecht; tglx@...utronix.de;
> x86@...nel.org; linux-kernel@...r.kernel.org; rusty@...tcorp.com.au;
> mingo@...hat.com
> Subject: unnecessary #ifdefs
> 
> Hi Feng Wu,
> 
> your commits
> 
> f6b3c72c23661e55 ("x86/irq: Define a global vector for VT-d
> Posted-Interrupts")
> 501b32653ebf49114c ("x86/irq: Show statistics information for
> posted-interrupts")
> 
> showed up in linux-next today (i.e. next-20150526).
> 
> Both commits add "#ifdef CONFIG_HAVE_KVM" blocks to either
> arch/x86/kernel/irq.c or arch/x86/include/asm/irq.h
> 
> However, HAVE_KVM is always enabled in x86, since the root option X86
> always selects HAVE_KVM.
> 
> How is the policy here, are these blocks inserted in case the "select
> HAVE_KVM" is removed from X86 someday or did you mean to use
> CONFIG_KVM?
> 

In fact, some of the "#ifdef CONFIG_HAVE_KVM" have been there for a while,
it was introduced for a special IPI for posted-interrupts used for KVM. Now we
need to add other similar IPI for posted-interrupts for KVM, so I just follow the
existing infrastructure. You can refer to commit " d78f2664832f8d70e36422af9a10e44276dced48 ",
where "#ifdef CONFIG_HAVE_KVM" was original used.

Thanks,
Feng

> 
> I detected the issue with undertaker-checkpatch [1, 2] running on a
> bot in Erlangen [3] to make daily checks of commits in linux-next for
> #ifdef related defects.
> 
> Best Regards,
> Stefan
> 
> [1] https://undertaker.cs.fau.de
> [2] http://www.linuxplumbersconf.org/2014/ocw/proposals/1863
> [3] https://cados.cs.fau.de