Re: [PATCH for-4.15] xen: Bump the minimum version of GCC supported to 4.9 (5.1 on arm64)

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Julien Grall writes ("[PATCH for-4.15] xen: Bump the minimum version of GCC 
supported to 4.9 (5.1 on arm64)"):
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> Compilers older than 4.8 have known codegen issues which can lead to
> silent miscompilation:
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145
> 
> Furthermore, pre-4.9 GCC have known bugs (including things like
> internal compiler errors on Arm) which would require workaround (I
> haven't checked if we have any in Xen).
> 
> The minimum version of GCC to build the hypervisor is now raised to 4.9.
> 
> In addition to that, on arm64, GCC version >= 4.9 and < 5.1 have been
> shown to emit memory references beyond the stack pointer, resulting in
> memory corruption if an interrupt is taken after the stack pointer has
> been adjusted but before the reference has been executed.
> 
> Therefore, the minimum for arm64 is raised to 5.1.

How sad.

Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>

I don't currently have an opinion about the merits of this change.
I'm hoping that the disagreement can be resolved without me having to
have one :-).

Thanks,
Ian.