[Xen-devel] [PATCH 15/20] xen/arm: mm: Use the shorter version __aligned(PAGE_SIZE) to align page-tables

[Julien Grall <julien.grall@xxxxxxx>]

We currently use the very long version __attribute__((__aligned(4096)))
to align page-tables. Thankfully there is a shorter version to make
the code more readable.

While modifying the attribute:
    1) Move it before the variable name as we do in other part of Xen
    2) Switch to PAGE_SIZE instead of 4096 to make more future-proof
    3) Mark static page-tables not used outside the file (i.e any
       page-tables other than boot_* and xen_fixmap).

Lastly, some of the variables use __attribute__(__aligned(X * 4096)).
However this is not necessary as page-tables are only required to be
to be aligned to a page-size. So use __aligned(PAGE_SIZE).

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
 xen/arch/arm/mm.c | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 6db7dda0da..fa0f41bd07 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -73,13 +73,13 @@ struct domain *dom_xen, *dom_io, *dom_cow;
  * Finally, if EARLY_PRINTK is enabled then xen_fixmap will be mapped
  * by the CPU once it has moved off the 1:1 mapping.
  */
-lpae_t boot_pgtable[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+lpae_t __aligned(PAGE_SIZE) boot_pgtable[LPAE_ENTRIES];
 #ifdef CONFIG_ARM_64
-lpae_t boot_first[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
-lpae_t boot_first_id[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+lpae_t __aligned(PAGE_SIZE) boot_first[LPAE_ENTRIES];
+lpae_t __aligned(PAGE_SIZE) boot_first_id[LPAE_ENTRIES];
 #endif
-lpae_t boot_second[LPAE_ENTRIES]  __attribute__((__aligned__(4096)));
-lpae_t boot_third[LPAE_ENTRIES]  __attribute__((__aligned__(4096)));
+lpae_t __aligned(PAGE_SIZE) boot_second[LPAE_ENTRIES];
+lpae_t __aligned(PAGE_SIZE) boot_third[LPAE_ENTRIES];
 
 /* Main runtime page tables */
 
@@ -93,8 +93,8 @@ lpae_t boot_third[LPAE_ENTRIES]  
__attribute__((__aligned__(4096)));
 
 #ifdef CONFIG_ARM_64
 #define HYP_PT_ROOT_LEVEL 0
-lpae_t xen_pgtable[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
-lpae_t xen_first[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+static lpae_t __aligned(PAGE_SIZE) xen_pgtable[LPAE_ENTRIES];
+static lpae_t __aligned(PAGE_SIZE) xen_first[LPAE_ENTRIES];
 #define THIS_CPU_PGTABLE xen_pgtable
 #else
 #define HYP_PT_ROOT_LEVEL 1
@@ -107,17 +107,16 @@ static DEFINE_PER_CPU(lpae_t *, xen_pgtable);
  * DOMHEAP_VIRT_START...DOMHEAP_VIRT_END in 2MB chunks. */
 static DEFINE_PER_CPU(lpae_t *, xen_dommap);
 /* Root of the trie for cpu0, other CPU's PTs are dynamically allocated */
-lpae_t cpu0_pgtable[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+static lpae_t __aligned(PAGE_SIZE) cpu0_pgtable[LPAE_ENTRIES];
 /* cpu0's domheap page tables */
-lpae_t cpu0_dommap[LPAE_ENTRIES*DOMHEAP_SECOND_PAGES]
-    __attribute__((__aligned__(4096*DOMHEAP_SECOND_PAGES)));
+static lpae_t __aligned(PAGE_SIZE) 
cpu0_dommap[LPAE_ENTRIES*DOMHEAP_SECOND_PAGES];
 #endif
 
 #ifdef CONFIG_ARM_64
 /* The first page of the first level mapping of the xenheap. The
  * subsequent xenheap first level pages are dynamically allocated, but
  * we need this one to bootstrap ourselves. */
-lpae_t xenheap_first_first[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+static lpae_t __aligned(PAGE_SIZE) xenheap_first_first[LPAE_ENTRIES];
 /* The zeroeth level slot which uses xenheap_first_first. Used because
  * setup_xenheap_mappings otherwise relies on mfn_to_virt which isn't
  * valid for a non-xenheap mapping. */
@@ -131,12 +130,12 @@ static __initdata int xenheap_first_first_slot = -1;
  * addresses from 0 to 0x7fffffff. Offsets into it are calculated
  * with second_linear_offset(), not second_table_offset().
  */
-lpae_t xen_second[LPAE_ENTRIES*2] __attribute__((__aligned__(4096*2)));
+static lpae_t __aligned(PAGE_SIZE) xen_second[LPAE_ENTRIES*2];
 /* First level page table used for fixmap */
-lpae_t xen_fixmap[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+lpae_t __aligned(PAGE_SIZE) xen_fixmap[LPAE_ENTRIES];
 /* First level page table used to map Xen itself with the XN bit set
  * as appropriate. */
-static lpae_t xen_xenmap[LPAE_ENTRIES] __attribute__((__aligned__(4096)));
+static lpae_t __aligned(PAGE_SIZE) xen_xenmap[LPAE_ENTRIES];
 
 /* Non-boot CPUs use this to find the correct pagetables. */
 uint64_t init_ttbr;
-- 
2.11.0


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