Messages in this thread | | | Date | Wed, 1 Oct 2008 09:11:38 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: do not allow to optimize flag_is_changeable_p() (rev. 2) |
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* Krzysztof Helt <krzysztof.h1@wp.pl> wrote:
> From: Krzysztof Helt <krzysztof.h1@wp.pl> > > The flag_is_changeable_p() is used by > has_cpuid_p() which can return different results > in the code sequence below: > > if (!have_cpuid_p()) > identify_cpu_without_cpuid(c); > > /* cyrix could have cpuid enabled via c_identify()*/ > if (!have_cpuid_p()) > return; > > Otherwise, the gcc 3.4.6 optimizes these two calls > into one which make the code not working correctly. > > Cyrix cpus have the CPUID instruction enabled before > the second call to the have_cpuid_p() but > it is not detected due to the gcc optimization. > Thus the ARR registers (mtrr like) are not detected > on such a cpu. > > Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
applied to tip/x86/core, thanks Krzysztof!
Ingo
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