Re: strange message appearing in a fresh current

so what should I do to get rid off the bug? I dont understand what are
you trying to tell me... thnx :)

On Sat, Jun 19, 2004 at 11:17:54PM +1000, Bruce Evans wrote:
> On Sat, 19 Jun 2004, Divacky Roman wrote:
> 
> > > > built for i686 cpu (amd duron) with -O -pipe
> > >
> > > Hmm.  Don't Durons have FXSR?  (I686_CPU or CPU_ENABLE_SSE) and not
> > > CPU_DISABLE_SSE together with a CPU that supports FXSR should give
> > > a configuration that is not affected by the bug.
> >
> >   Origin = "AuthenticAMD"  Id = 0x631  Stepping = 1
> >     Features=0x183f9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,MMX,FXSR>
> >       AMD Features=0xc0440000<RSVD,AMIE,DSP,3DNow!>
> >
> > I just set
> > cpu             I686_CPU
> >
> > no CPU_* at all. And the bug is there...
> 
> Ah.  It needs SSE in the cpuid too, and your Duron doesn't have it.  I
> think Athlons got SSE starting with the XP.
> 
> The configuration of this is confusing.  From i386/initcpu.c:
> 
> % #if !defined(CPU_ENABLE_SSE) && defined(I686_CPU)
> % #define CPU_ENABLE_SSE
> % #endif
> % #if defined(CPU_DISABLE_SSE)
> % #undef CPU_ENABLE_SSE
> % #endif
> 
> So I686_CPU gives CPU_ENABLE_SSE unless you use CPU_DISABLE_SSE.
> 
> % /*
> %  * Initialize CR4 (Control register 4) to enable SSE instructions.
> %  */
> % void
> % enable_sse(void)
> % {
> % #if defined(CPU_ENABLE_SSE)
> % 	if ((cpu_feature & CPUID_XMM) && (cpu_feature & CPUID_FXSR)) {
> % 		load_cr4(rcr4() | CR4_FXSR | CR4_XMM);
> % 		cpu_fxsr = hw_instruction_sse = 1;
> % 	}
> % #endif
> % }
> 
> Here CPUID_XMM is a confusing alias for CPUID_SSE (the identifcation message
> only prints "SSE").  So to get cpu_fxsr, you need CPU_ENABLE_SSE or
> I686_CPU && !CPU_DISABLE_SSE in the FreeBSD config, and SSE and FXSR in
> the hardware.
> 
> % 		} else if (strcmp(cpu_vendor, "AuthenticAMD") == 0) {
> % #if defined(I686_CPU) && defined(CPU_ATHLON_SSE_HACK)
> % 			/*
> % 			 * Sometimes the BIOS doesn't enable SSE instructions.
> % 			 * According to AMD document 20734, the mobile
> % 			 * Duron, the (mobile) Athlon 4 and the Athlon MP
> % 			 * support SSE. These correspond to cpu_id 0x66X
> % 			 * or 0x67X.
> % 			 */
> % 			if ((cpu_feature & CPUID_XMM) == 0 &&
> % 			    ((cpu_id & ~0xf) == 0x660 ||
> % 			     (cpu_id & ~0xf) == 0x670 ||
> % 			     (cpu_id & ~0xf) == 0x680)) {
> % 				u_int regs[4];
> % 				wrmsr(0xC0010015, rdmsr(0xC0010015) & ~0x08000);
> % 				do_cpuid(1, regs);
> % 				cpu_feature = regs[3];
> % 			}
> % #endif
> 
> And for broken BIOSes, CPU_ATHLON_SSE_HACK is also needed to get SSE.
> 
> Bruce