Messages in this thread | | | Date | Wed, 18 May 2011 04:46:43 +0200 | Subject | Re: [PATCH 2/9] x86/kernel/cpu/intel.c: Initialize Enhanced REP MOVSB/STOSBenhanced | From | "Andi Kleen" <> |
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> From: Fenghua Yu <fenghua.yu@intel.com> > > If kernel intends to use enhanced REP MOVSB/STOSB, it must ensure > IA32_MISC_ENABLE.Fast_String_Enable (bit 0) is set and CPUID.(EAX=07H, > ECX=0H): > EBX[bit 9] also reports 1.
I suspect the check at this place is not too useful because it will only work for the BSP. For all others it's too late -- the patching has already happened.
So either this is a problem and then it should be checked on all CPUs. Or maybe not at all.
The problem is that the alternative patching currently relies on being run early with no other CPUs. It has no race protections, support for cross modification etc.
While it would be possible to fix that it would be quite complicated I bet.
So I think it's better to just remove it unless it's a real problem in the field.
-Andi
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