Re: [Xen-devel] [PATCH] xen/x86: clear per cpu stub page information in cpu_smpboot_free()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.01.2020 12:01, Juergen Gross wrote:
> --- a/xen/arch/x86/smpboot.c
> +++ b/xen/arch/x86/smpboot.c
> @@ -945,6 +945,8 @@ static void cpu_smpboot_free(unsigned int cpu, bool 
> remove)
>                               (per_cpu(stubs.addr, cpu) | ~PAGE_MASK) + 1);
>          if ( i == STUBS_PER_PAGE )
>              free_domheap_page(mfn_to_page(mfn));
> +        per_cpu(stubs.addr, cpu) = 0;
> +        per_cpu(stubs.mfn, cpu) = 0;
>      }

Afaict this was a regression from the introduction of CPU parking:
Prior to that, per-CPU data would have been zeroed in all cases
before a new CPU was unleashed. I think it would be helpful it
this was mentioned in the description (possibly by way of a Fixes:
tag).

Jan

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