Messages in this thread | | | Date | Mon, 21 Apr 2008 10:22:47 -0400 | From | "H. Peter Anvin" <> | Subject | Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5) |
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Pavel Machek wrote: > On Thu 2008-04-17 16:14:10, Mathieu Desnoyers wrote: >> (hopefully finally CCing LKML) :) >> >> Implements an alternative iret with popf and return so trap and exception >> handlers can return to the NMI handler without issuing iret. iret would cause >> NMIs to be reenabled prematurely. x86_32 uses popf and far return. x86_64 has to >> copy the return instruction pointer to the top of the previous stack, issue a >> popf, loads the previous esp and issue a near return (ret). > > sounds expensive. Does it slow down normal loads? >
It should *only* be used to return from NMI, #MC or INT3 (breakpoint), which should never happen in normal operation, and even then only when interrupting another NMI or #MC handler.
-hpa
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