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SubjectRe: [PATCH 01/22] ARM: add mechanism for late code patching
On Tue, Jul 31, 2012 at 07:04:37PM -0400, Cyril Chemparathy wrote:
> +static void __init init_patch_kernel(void)
> +{
> + const void *start = &__patch_table_begin;
> + const void *end = &__patch_table_end;
> +
> + BUG_ON(patch_kernel(start, end - start));
> + flush_icache_range(init_mm.start_code, init_mm.end_code);

Err. You are asking the kernel to flush every single cache line
manually throughout the kernel code. That's a flush every 32-bytes
over maybe a few megabytes of address space.

This is one of the reasons we do the patching in assembly code before
the caches are enabled - so we don't have to worry about the interaction
with the CPU caches, which for this kind of application would be very
expensive.


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