Re: [Xen-devel] [PATCH 1/2] xen/link: Introduce .bss.percpu.page_aligned

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jul 26, 2019 at 02:52:39PM +0100, Andrew Cooper wrote:
> Future changes are going to need to page align some percpu data.
> 
> This means that the percpu area needs suiably aligning in the BSS so CPU0 has
> correctly aligned data.  Shuffle the exact link order of items within the BSS
> to give .bss.percpu.page_aligned appropriate alignment.
> 
> Additionally, introduce DEFINE_PER_CPU_PAGE_ALIGNED()
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien.grall@xxxxxxx>
> CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
> ---
>  xen/arch/arm/xen.lds.S   | 5 +++--
>  xen/arch/x86/xen.lds.S   | 5 +++--
>  xen/include/xen/percpu.h | 2 ++
>  3 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
> index 12c107f45d..07cbdf2543 100644
> --- a/xen/arch/arm/xen.lds.S
> +++ b/xen/arch/arm/xen.lds.S
> @@ -201,14 +201,15 @@ SECTIONS
>         *(.bss.stack_aligned)
>         . = ALIGN(PAGE_SIZE);
>         *(.bss.page_aligned)
> -       *(.bss)
> -       . = ALIGN(SMP_CACHE_BYTES);

Don't you also need a:

. = ALIGN(PAGE_SIZE);

here? Or is the size of .bss.page_aligned also aligned to page size?

Thanks, Roger.

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