linux-kernel - Re: [PATCH] apic: fix kvm build on UP without IOAPIC

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Message-ID: <20120703185511.GA24415@amt.cnet>
Date:	Tue, 3 Jul 2012 15:55:11 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Avi Kivity <avi@...hat.com>, Randy Dunlap <rdunlap@...otime.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>, x86@...nel.org,
	kvm@...r.kernel.org, linux-next@...r.kernel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] apic: fix kvm build on UP without IOAPIC

On Sun, Jul 01, 2012 at 06:05:06PM +0300, Michael S. Tsirkin wrote:
> On UP i386, when APIC is disabled
> # CONFIG_X86_UP_APIC is not set
> # CONFIG_PCI_IOAPIC is not set
> 
> code looking at apicdrivers never has any effect but it
> still gets compiled in. In particular, this causes
> build failures with kvm, but it generally bloats the kernel
> unnecessarily.
> 
> Fix by defining both __apicdrivers and __apicdrivers_end
> to be NULL when CONFIG_X86_LOCAL_APIC is unset: I verified
> that as the result any loop scanning __apicdrivers gets optimized out by
> the compiler.
> 
> Warning: a .config with apic disabled doesn't seem to boot
> for me (even without this patch). Still verifying why,
> meanwhile this patch is compile-tested only.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> 
> Note: if this patch makes sense, can x86 maintainers
> please ACK applying it through the kvm tree, since that is
> where we see the issue that it addresses?
> Avi, Marcelo, maybe you can carry this in kvm/linux-next as a temporary
> measure so that linux-next builds?

Applied, thanks.

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