--- Begin Message ---
- To: [email protected]
- Subject: Bogus PNI flag in /proc/cpuinfo
- From: Dario Birtic <[email protected]>
- Date: Thu, 28 Apr 2005 00:05:58 +0200
- User-agent: Mozilla Thunderbird 1.0.2 (X11/20050424)
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Hello,
I am expiriencing bogus PNI /proc/cpuinfo flag (and as far I can tell,
out of plenty of auxillary /proc/cpuinfo flags I have seen on the
internet, everyone having the athlon64 architecture also):
cat /proc/cpuinfo
processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 15
model name : AMD Athlon(tm) 64 Processor 3500+
stepping : 0
cpu MHz : 2340.189
cache size : 512 KB
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
mca cmov pat pse36 clflush mmx fxsr sse sse2 pni syscall nx mmxext lm
3dnowext 3dnow
bogomips : 4636.67
TLB size : 1024 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management: ts fid vid ttp
Though this processor doesn't support PNI (aka SSE3) it is reported in
the flags.
cat /proc/version
Linux version 2.6.11-gentoo-r6 (root@beast) (gcc version 3.4.3 20041125
(Gentoo Linux 3.4.3-r1, ssp-3.4.3-0, pie-8.7.7)) #2 Mon Apr 25 00:34:25
CEST 2005
I am expiriencing this behaviour since cca. 2.6.8.1.
A simple testcase shows:
cat << "EOF" > test_pni.c
#include <stdint.h>
uint8_t __attribute__((aligned(64))) current[64];
uint8_t previous[64];
int main()
{
int i;
uint64_t result;
uint32_t _eax, _ebx, _ecx, _edx;
uint8_t _cpuid[13];
uint32_t *_cpuid0 = (uint32_t*) _cpuid;
uint32_t *_cpuid1 = (uint32_t*) ( _cpuid + 4 );
uint32_t *_cpuid2 = (uint32_t*) ( _cpuid + 8 );
uint8_t *ptr0 = current;
uint8_t *ptr1 = previous;
__asm__ __volatile__ (
"cpuid\n"
: "=a" (_eax),
"=b" (*_cpuid0), "=d" (*_cpuid1), "=c" (*_cpuid2)
: "a" (0) );
_cpuid[12] = 0;
printf( "cpuid(0) returns %d (%s)\n", _eax, _cpuid );
__asm__ __volatile__ (
"cpuid\n"
: "=a" (_eax), "=b" (_ebx), "=c" (_ecx), "=d" (_edx)
: "a" (1) );
printf( "cpuid(1) returns %08x %08x %08x %08x\n",
_eax, _ebx, _ecx, _edx );
memset( current, 0xaa, 64 );
memset( previous, 0x55, 64 );
for( i = 0; i < 4; i ++ ) {
__asm__ __volatile__ (
"movdqa %0, %%xmm0\n"
"movdqu %1, %%xmm1\n"
"psadbw %%xmm1, %%xmm0\n"
"paddw %%xmm0, %%xmm2\n"
"haddps %%xmm2, %%xmm2\n"
"haddps %%xmm2, %%xmm2\n"
: : "m" (*ptr0),
"m" (*ptr1) : "xmm0", "xmm1", "xmm2" );
ptr0 += 16;
ptr1 += 16;
}
__asm__ __volatile__ (
"movq %%xmm2, %0\n"
: "=m" (result) );
printf( "Result is %llu\n", result );
}
EOF
gcc -o test_pni test_pni.c
./test_pni
cpuid(0) returns 1 (AuthenticAMD)
cpuid(1) returns 00000ff0 00000800 00000000 078bfbff
Illegal instruction
This is expected since there is no PNI on this processor supported
(haddps being SSE3 instruction). Please also note that ECX bit 0 (PNI
support) is clear showing that SSE3 is *not* supported.
Regards
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