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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Tue, 5 Apr 2016 17:29:05 +0200
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Subject: Re: [Qemu-devel] [PATCH 02/10] compiler.h: add QEMU_CACHELINE +
 QEMU_ALIGN() + QEMU_CACHELINE_ALIGNED
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To: Peter Maydell <peter.maydell@linaro.org>, "Emilio G. Cota" <cota@braap.org>, QEMU Developers <qemu-devel@nongnu.org>, MTTCG Devel <mttcg@greensocs.com>, Peter Crosthwaite <crosthwaite.peter@gmail.com>, Sergey Fedorov <serge.fdrv@gmail.com>, =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Richard Henderson <rth@twiddle.net>



On 05/04/2016 14:58, Peter Maydell wrote:
>> >
>> > You should make this a value taken from configure. In linux you coul=
d use
>> > something like:
>> >
>> >   getconf LEVEL1_DCACHE_LINESIZE
>> >
>> > Or an equivalent program using sysconf(3) if getconf is not present.
> The cache line size at compile time is not necessarily the cache
> line size at runtime...

But the size of data structures cannot change at run-time.  A bigger
worry is cross-compilation.

Linux has these defaults:

	Alpha	32 or 64
	ARM	configurable, 64 for ARMv7
	AArch64	128
	PPC     128
	s390	256
	x86	configurable, default 64

which should be easy to copy in QEMU too.

Paolo