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

[Andi Kleen <ak@xxxxxx>]

"Nakajima, Jun" <jun.nakajima@xxxxxxxxx> writes:

> Long mode needs to align the stack on a 16-byte boundary. Recent changes
> to Xen broke the requirement, and x86-64 XenLinux stopped booting. The
> attached fixes the problem. 

Normally it should be only needed in user space for saving FP registers.
The kernel and Xen which should not do this probably don't need it.

Unless you save FP registers on the stack somewhere. Then I would
rather fix that place only.

At least the main linux kernel does not try to keep the stack
always 16byte aligned. There is even a gcc option to turn it off
and it saves some code (and probably stack) size.

-Andi

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