• Mark Rutland's avatar
    arm64: head.S: ensure visibility of page tables · 91d57155
    Mark Rutland authored
    
    
    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: default avatarMark Rutland <mark.rutland@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Fixes: c218bca7
    
     ("arm64: Relax the kernel cache requirements for boot")
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    91d57155
head.S 18.2 KB