[PATCH 2/2] arm64:acpi Fix the acpi alignment exeception when 'mem=' specified
Mark Rutland
mark.rutland at arm.com
Thu Jun 23 05:42:30 PDT 2016
On Thu, Jun 23, 2016 at 07:30:15PM +0800, Dennis Chen wrote:
> This is a rework patch based on [1]. According to the proposal from
> Mark Rutland, when applying the system memory limit through 'mem=x'
> kernel command line, don't remove the rest memory regions above the
> limit from the memblock, instead marking them as MEMBLOCK_NOMAP region,
> which will preserve the ability to identify regions as normal memory
> while not using them for allocation and the linear map.
>
> Without this patch, the ACPI core will map those acpi data regions(if
> they are above the limit) as device type memory, which will result in
> the alignment exception when ACPI core parses the AML data stream
> since the parsing will produce some non-alignment accesses.
>
> [1]:http://lists.infradead.org/pipermail/linux-arm-kernel/2016-June/438443.html
Please rewrite the message to be standalone (i.e. so peopel can read
this without having to folow the link).
Explain why using mem= makes ACPI think regions should be mapped as
Device memory, the problems this causes for ACPICA, then cover why we
want to nomap the region.
> Signed-off-by: Dennis Chen <dennis.chen at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Steve Capper <steve.capper at arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> Cc: Matt Fleming <matt at codeblueprint.co.uk>
> Cc: linux-mm at kvack.org
> Cc: linux-acpi at vger.kernel.org
> Cc: linux-efi at vger.kernel.org
> ---
> arch/arm64/mm/init.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index d45f862..e509e24 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -222,12 +222,14 @@ void __init arm64_memblock_init(void)
>
> /*
> * Apply the memory limit if it was set. Since the kernel may be loaded
> - * high up in memory, add back the kernel region that must be accessible
> - * via the linear mapping.
> + * in the memory regions above the limit, so we need to clear the
> + * MEMBLOCK_NOMAP flag of this region to make it can be accessible via
> + * the linear mapping.
> */
> if (memory_limit != (phys_addr_t)ULLONG_MAX) {
> - memblock_enforce_memory_limit(memory_limit);
> - memblock_add(__pa(_text), (u64)(_end - _text));
> + memblock_mem_limit_mark_nomap(memory_limit);
> + if (!memblock_is_map_memory(__pa(_text)))
> + memblock_clear_nomap(__pa(_text), (u64)(_end - _text));
I think that the memblock_is_map_memory() check should go. Just because
a page of the kernel image is mapped doesn't mean that the rest is. That
will make this a 1-1 change.
Other than that, this looks right to me.
Thanks,
Mark.
> }
>
> if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) {
> --
> 1.8.3.1
>
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