On Thu, Jul 11, 2002 at 02:46:24AM -0600, Eric Anholt wrote:
> A while ago I added the stuff to the config/cf/* to enable USE_SSE_ASM
> on FreeBSD, but today found that it wasn't enabled on my athlon. I
> added the proper sysctl check for it, but it still wasn't enabled. It
> turns out the Athlon's extended CPUID function has most of the same
> feature bits as the standard CPUID features function, but it doesn't
> ever enable the SSE bit. I've made a patch that ORs in the bit from the
> standard function, enabling SSE on new Athlons. It's attached.
A better fix would be to actually enable SSE before FreeBSD does its
feature flag detection. Linux does the following very early on..
/* Bit 15 of Athlon specific MSR 15, needs to be 0
* to enable SSE on Palomino/Morgan CPU's.
* If the BIOS didn't enable it already, enable it
* here.
*/
if (c->x86_model == 6 || c->x86_model == 7) {
if (!cpu_has(c, X86_FEATURE_XMM)) {
printk(KERN_INFO "Enabling disabled K7/SSE Support.\n");
rdmsr(MSR_K7_HWCR, l, h);
l &= ~0x00008000;
wrmsr(MSR_K7_HWCR, l, h);
set_bit(X86_FEATURE_XMM, c->x86_capability);
}
}
Seems some BIOSen didn't enable this magical bit. Your patch is just
doing the FreeBSD equivalent of the set_bit() call above, which is
fine for anything that parses those flags, but breaks any userspace
that does its own cpuid() calls to find out cpu capabilities.
Dave
--
| Dave Jones. http://www.codemonkey.org.uk
| SuSE Labs
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