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[PATCH] x86/boot: move l<N>_bootmap
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 25 Jun 2025 11:05:47 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 25 Jun 2025 09:05:58 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Having them in the general .init.data section is somewhat wasteful, due
to involved padding. Move them into .init.data.page_aligned, and place
that right after .init.bss.stack_aligned.
Overall .init.data* shrinks by slightly over 2 pages in the build I'm
looking at.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
All three tables are merely zero-filled. They could hence even be put in
.init.bss.page_aligned, yet then we perhaps better wouldn't use .fill
but .skip there (i.e. a larger diff for little gain). Thoughts?
--- a/xen/arch/x86/boot/x86_64.S
+++ b/xen/arch/x86/boot/x86_64.S
@@ -193,7 +193,7 @@ END(idle_pg_table)
GLOBAL(__page_tables_end)
/* Init pagetables. Enough page directories to map into 4GB. */
- .section .init.data, "aw", @progbits
+ .section .init.data.page_aligned, "aw", @progbits
DATA_LOCAL(l1_bootmap, PAGE_SIZE)
.fill L1_PAGETABLE_ENTRIES, 8, 0
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -221,6 +221,7 @@ SECTIONS
DECL_SECTION(.init.data) {
#endif
*(.init.bss.stack_aligned)
+ *(.init.data.page_aligned)
. = ALIGN(POINTER_ALIGN);
__initdata_cf_clobber_start = .;
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