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arm64: head.S: ensure visibility of page tables 

After writing the page tables, we use __inval_cache_range to invalidate
any stale cache entries. Strongly Ordered memory accesses are not
ordered w.r.t. cache maintenance instructions, and hence explicit memory
barriers are required to provide this ordering. However,
__inval_cache_range was written to be used on Normal Cacheable memory
once the MMU and caches are on, and does not have any barriers prior to
the DC instructions.

This patch adds a DMB between the page tables being written and the
corresponding cachelines being invalidated, ensuring that the
invalidation makes the new data visible to subsequent cacheable
accesses. A barrier is not required before the prior invalidate as we do
not access the page table memory area prior to this, and earlier
barriers in preserve_boot_args and set_cpu_boot_mode_flag ensures
ordering w.r.t. any stores performed prior to entering Linux.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: c218bca74e ("arm64: Relax the kernel cache requirements for boot")
Signed-off-by: Will Deacon <will.deacon@arm.com>
hifive-unleashed-5.1
Mark Rutland 2015-03-24 13:50:27 +00:00 committed by Will Deacon
parent e4c5a68510
commit 91d57155dc
1 changed files with 1 additions and 0 deletions
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arch/arm64/kernel/head.S
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@ -458,6 +458,7 @@ __create_page_tables:
*/
mov x0, x25
add x1, x26, #SWAPPER_DIR_SIZE
dmb sy
bl __inval_cache_range
mov lr, x27