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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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);
        __per_cpu_start = .;
+       *(.bss.percpu.page_aligned)
        *(.bss.percpu)
        . = ALIGN(SMP_CACHE_BYTES);
        *(.bss.percpu.read_mostly)
        . = ALIGN(SMP_CACHE_BYTES);
        __per_cpu_data_end = .;
+       *(.bss)
+       . = ALIGN(SMP_CACHE_BYTES);
        __bss_end = .;
   } :text
   _end = . ;
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index a73139cd29..b8a2ea4259 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -293,14 +293,15 @@ SECTIONS
        __bss_start = .;
        *(.bss.stack_aligned)
        *(.bss.page_aligned*)
-       *(.bss)
-       . = ALIGN(SMP_CACHE_BYTES);
        __per_cpu_start = .;
+       *(.bss.percpu.page_aligned)
        *(.bss.percpu)
        . = ALIGN(SMP_CACHE_BYTES);
        *(.bss.percpu.read_mostly)
        . = ALIGN(SMP_CACHE_BYTES);
        __per_cpu_data_end = .;
+       *(.bss)
+       . = ALIGN(SMP_CACHE_BYTES);
        __bss_end = .;
   } :text
   _end = . ;
diff --git a/xen/include/xen/percpu.h b/xen/include/xen/percpu.h
index aeec5c19d6..c5291dc5e9 100644
--- a/xen/include/xen/percpu.h
+++ b/xen/include/xen/percpu.h
@@ -10,6 +10,8 @@
  * macro expanded, while still allowing a per-architecture symbol name prefix.
  */
 #define DEFINE_PER_CPU(type, name) __DEFINE_PER_CPU(type, _##name, )
+#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
+       __DEFINE_PER_CPU(type, _##name, .page_aligned)
 #define DEFINE_PER_CPU_READ_MOSTLY(type, name) \
        __DEFINE_PER_CPU(type, _##name, .read_mostly)
 
-- 
2.11.0


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