Re: [Xen-devel] [PATCH v2] x86/boot: Rationalise stack handling during early boot

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.01.2020 12:51, Andrew Cooper wrote:
> The top (numerically higher addresses) of cpu0_stack[] contains the BSP's
> cpu_info block.  Logic in Xen expects this to be initialised to 0, but this
> area of stack is also used during early boot.
> 
> Update the head.S code to avoid using the cpu_info block.  Additionally,
> update the stack_start variable to match, which avoids __high_start() and
> efi_arch_post_exit_boot() needing to make the adjustment manually.
> 
> Finally, leave a big warning by the BIOS BSS initialisation, because it is by
> no means obvious that the stack doesn't survive the REP STOS.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

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