On Tue, Aug 09, 2016 at 09:35:54AM -0700, Thomas Garnier wrote:
> Default implementation expects 6 pages maximum are needed for low page
> allocations. If KASLR memory randomization is enabled, the worse case
> of e820 layout would require 12 pages (no large pages). It is due to the
> PUD level randomization and the variable e820 memory layout.
>
> This bug was found while doing extensive testing of KASLR memory
> randomization on different type of hardware.
>
> Fixes: 021182e52fe0 ("Enable KASLR for physical mapping memory regions")
> Signed-off-by: Thomas Garnier <[email protected]>
> ---
> Based on next-20160805
> ---
> arch/x86/mm/init.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 6209289..796e7af 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -122,8 +122,18 @@ __ref void *alloc_low_pages(unsigned int num)
> return __va(pfn << PAGE_SHIFT);
> }
>
> -/* need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS */
> -#define INIT_PGT_BUF_SIZE (6 * PAGE_SIZE)
> +/*
> + * By default need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS.
> + * With KASLR memory randomization, depending on the machine e860 memory
> layout
> + * and the PUD alignement. We may need twice more pages when KASLR memoy
> + * randomization is enabled.
Can you please integrate all review feedback before you send your next
versions?
There's no "e860" thing and
s/memoy/memory/ and
s/alignement/alignment/
IOW, just integrate a spellchecker into your workflow.
Thanks.
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Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
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