Re: [PATCH 3/4] x86,asm: Re-work smp_store_mb()

From: Borislav Petkov
Date: Wed Jan 13 2016 - 11:53:40 EST


On Wed, Jan 13, 2016 at 06:42:48PM +0200, Michael S. Tsirkin wrote:
> Oh, I think this means we need a "cc" clobber.

Btw, does your microbenchmark do it too?

Because, the "cc" clobber should cause additional handling of flags,
depending on the context. It won't matter if the context doesn't need
rFLAGS handling in the benchmark but if we start using LOCK; ADD in the
kernel, I can imagine some places where mb() is used and rFLAGS are
live, causing gcc to either reorder code or stash them away...

--
Regards/Gruss,
Boris.

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