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

From: H. Peter Anvin
Date: Sun Jul 01 2012 - 13:11:05 EST

On 07/01/2012 08:05 AM, 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

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@xxxxxxxxxx>

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?

I'm not happy about that as a workflow, but since you guys have an immediate problem I guess we can do that.

Acked-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>


H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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