[Xen-devel] Re: [PATCH] Fixing stack alignment in x86-64 Xen

[Andi Kleen <ak@xxxxxx>]

"Nakajima, Jun" <jun.nakajima@xxxxxxxxx> writes:
>
> The recent optimization reset_stack_and_jump() code needs to know the
> exact address of the interrupt stack (because it resets %rsp), and
> calculates it based on the value that Xen set (i.e. 8-byte boundary).
> Since the processor forces the rsp0 on a 16-byte boundary (i.e. moves it
> down by 8 bytes), Xen sees a wrong stack when returning from the
> interrupt.

I would rather fix reset_stack_and_jump then to do the necessary
rounding or better look at the original RSP the processor stored into the
stack frame. Otherwise the 16 byte alignment will probably bite you
later again.

-Andi

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