Re: [RFC/INCOMPLETE 08/13] x86/entry/64: Migrate 64-bit syscalls to new exit hooks

From: Ingo Molnar
Date: Thu Jun 18 2015 - 06:17:23 EST

* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> >> Any reason why irq state tracking cannot be done in C as well, like the rest
> >> of the irq state tracking code?
> >
> > Never mind, I see you've done exactly that in patch #12.
> There are still some TRACE_IRQS_ON, LOCKDEP_SYS_EXIT, and such scattered
> throughout the asm. it's plausible that even more of that could be moved to C.
> We could also benchmark and find out how bad it would be if we just always
> filled pt_regs in completely in syscalls. If the performance hit isn't enough
> to matter, then we could potentially move the entire syscall path except pt_regs
> setup and sysret/iret into three C functions.

The thing is, I'd not be against simplifying pt_regs handling even if it slows
down things a tiny bit. If anyone wants to reintroduce that complexity we'll see
how it looks like in isolation, done cleanly.


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