[Xen-devel] IA32: init_xen_time potential bug

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Subject:	[Xen-devel] IA32: init_xen_time potential bug
From:	"Dong, Eddie" <eddie.dong@xxxxxxxxx>
Date:	Thu, 28 Apr 2005 13:46:58 +0800
Delivery-date:	Thu, 28 Apr 2005 05:46:56 +0000
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Thread-topic:	IA32: init_xen_time potential bug

Hi:
        The following code in init_xen_time of file arch/x86/time.c have
potential problem to support any cpu_freq >= 4GHZ, as the variable scale
is in u64 format and will overflow when rdtsc_bitshift > 2. I am
doubting the necessary of rdtsc_bitshift, introducing this conecpt has
no obvious benefit but will slow down the interrupt handler. 
Eddie


    cpu_ghz = (unsigned int)(cpu_freq / 1000000000ULL);
    for ( rdtsc_bitshift = 0; cpu_ghz != 0; rdtsc_bitshift++, cpu_ghz
>>= 1 )
        continue;

    scale  = 1000000000LL << (32 + rdtsc_bitshift);
    scale /= cpu_freq;

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[Xen-devel] IA32: init_xen_time potential bug