MFC: r274054 (missed in r276076)

Fix XEN kernel build.

MFC 271405,271408,271409,272658:
MFamd64: Use initializecpu() to set various model-specific registers on
AP startup and AP resume (it was already used for BSP startup and BSP
resume).

Merge r264984

Retire smp_active. It was racey and caused demonstrated problems with
the cpufreq code. Replace its use with smp_started. There's at least
one userland tool that still looks at the kern.smp.active sysctl, so
preserve it but point it to smp_started as well.

Obtained from: Netflix, Inc.

MFC r263001

Move asm IPIs handlers to C code, so both Xen and native IPI handlers
share the same code.

Approved by: gibbs
Sponsored by: Citrix Systems R&D

MFC: r274054 (missed in r276076)

Fix XEN kernel build.

MFC 271405,271408,271409,272658:
MFamd64: Use initializecpu() to set various model-specific registers on
AP startup and AP resume (it was already used for BSP startup and BSP
resume).

Merge r264984

Retire smp_active. It was racey and caused demonstrated problems with
the cpufreq code. Replace its use with smp_started. There's at least
one userland tool that still looks at the kern.smp.active sysctl, so
preserve it but point it to smp_started as well.

Obtained from: Netflix, Inc.

MFC r263001

Move asm IPIs handlers to C code, so both Xen and native IPI handlers
share the same code.

Approved by: gibbs
Sponsored by: Citrix Systems R&D