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Re: [Xen-devel] [PATCH v3 1/2] xen/link: Introduce .bss.percpu.page_aligned
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <JBeulich@xxxxxxxx>
- Date: Tue, 30 Jul 2019 08:42:37 +0000
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- Cc: StefanoStabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 30 Jul 2019 08:55:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHVRjSGjfvYvY8Mj0+dnjT7dlU+s6bi2QqA
- Thread-topic: [PATCH v3 1/2] xen/link: Introduce .bss.percpu.page_aligned
On 29.07.2019 19:38, Andrew Cooper wrote:
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -293,14 +293,17 @@ SECTIONS
> __bss_start = .;
> *(.bss.stack_aligned)
> *(.bss.page_aligned*)
> - *(.bss)
> - . = ALIGN(SMP_CACHE_BYTES);
> + . = ALIGN(PAGE_SIZE);
> __per_cpu_start = .;
> + *(.bss.percpu.page_aligned)
> + . = ALIGN(PAGE_SIZE);
But this goes too far: What we want is for the TSS to occupy a full
page, not for whatever random other page-aligned object ends up
last here (should any every appear). If you want to effect this
via linker script (rather than C arrangements), then just like the
CPU0 stack I think we want a dedicated section containing _just_
the TSS. (Having said that I realize that .bss.stack_aligned isn't
really a good name for a dedicated section. It's just that we
obviously want the stack to occupy its entire STACK_SIZE range. Of
course we could put ourselves on the position that
.bss.percpu.page_aligned too _is_ a dedicated section despite its
name, but if you mean it to be like that then it would be nice for
the description to actually say so.)
Jan
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