On Thu, Jun 23, 2016 at 01:42:30PM +0100, Mark Rutland wrote: > 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@xxxxxxx> > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > > Cc: Steve Capper <steve.capper@xxxxxxx> > > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > > Cc: Will Deacon <will.deacon@xxxxxxx> > > Cc: Mark Rutland <mark.rutland@xxxxxxx> > > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> > > Cc: linux-mm@xxxxxxxxx > > Cc: linux-acpi@xxxxxxxxxxxxxxx > > Cc: linux-efi@xxxxxxxxxxxxxxx > > --- > > 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. > Good catch! Will be applied, thanks! > > Other than that, this looks right to me. > > Thanks, > Mark. > > > } > > > > if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_start) { > > -- > > 1.8.3.1 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
