backport 2.6 x86 cpu capabilities

2.4.21-rc1 with NCAPINTS==6 hangs at boot in the local APIC timer calibration step; before that it detected a 0MHz bus clock and the local APIC NMI watchdog was stuck. Correcting head.S:X86_VENDOR_ID fixes these problems.

Without correcting head.S:X86_VENDOR_ID, head.S will store the vendor id partly in the capabilities array. This breaks both the capabilities and the vendor id. I can't say why 2.6 works, but obviously the CPU setup code has changed since 2.4.

Quoted 9 lines · Mikael Pettersson

2.4.21-rc1 with NCAPINTS==6 hangs at boot in the local APIC timer calibration step; before that it detected a 0MHz bus clock and the local APIC NMI watchdog was stuck. Correcting head.S:X86_VENDOR_ID fixes these problems.

Without correcting head.S:X86_VENDOR_ID, head.S will store the vendor id partly in the capabilities array. This breaks both the capabilities and the vendor id. I can't say why 2.6 works, but obviously the CPU setup code has changed since 2.4.

I may be stating the obvious, but in case not...

If Jeff Garzik missed this, others will too. I hope that a big comment gets added in both places, assuming that automatic offset generation isn't practical.