Re: [PATCH v3] drivers/char: kmem: disable on arm64

From: Ard Biesheuvel
Date: Mon Jul 17 2017 - 13:05:10 EST


On 17 July 2017 at 15:18, gregkh@xxxxxxxxxxxxxxxxxxx
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Jun 20, 2017 at 01:20:49PM +0200, Ard Biesheuvel wrote:
>> On 20 June 2017 at 08:59, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
>> > As it turns out, arm64 deviates from other architectures in the way it
>> > maps the VMALLOC region: on most (all?) other architectures, it resides
>> > strictly above the kernel's direct mapping of DRAM, but on arm64, this
>> > is the other way around. For instance, for a 48-bit VA configuration,
>> > we have
>> >
>> > modules : 0xffff000000000000 - 0xffff000008000000 ( 128 MB)
>> > vmalloc : 0xffff000008000000 - 0xffff7dffbfff0000 (129022 GB)
>> > ...
>> > vmemmap : 0xffff7e0000000000 - 0xffff800000000000 ( 2048 GB maximum)
>> > 0xffff7e0000000000 - 0xffff7e0003ff0000 ( 63 MB actual)
>> > memory : 0xffff800000000000 - 0xffff8000ffc00000 ( 4092 MB)
>> >
>> > This has mostly gone unnoticed until now, but it does appear that it
>> > breaks an assumption in the kcore
>>
>> s/kcore/kmem/
>
> v4? :)
>

This is already in mainline as 06c35ef1fdf8d955684448683f7e48ac5f15ccfd