port-amd64/37662: amd64 nmi handler is broken

[yamt%mwd.biglobe.ne.jp@localhost]

>Number:         37662
>Category:       port-amd64
>Synopsis:       amd64 nmi handler is broken
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    port-amd64-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 01 22:20:00 +0000 2008
>Originator:     YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>Release:        NetBSD 4.99.47
>Organization:
        
>Environment:
System: NetBSD 4.99.47
Architecture: amd64
>Description:
        amd64 nmi handler can use inappropriate stack
        if an nmi happens at eg. the top of Xsyscall.
>How-To-Repeat:
        code inspection.
>Fix:
        - allocate per-cpu stacks, and use IST to switch to the stack.
        - make tss per-cpu.  (otherwise context switch needs to update IST.)

>Unformatted: