linux-kernel - Re: [PATCH 1/2] numa: Add simple generic NUMA emulation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Wed, 26 Jun 2024 12:47:33 +0100
From: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Tvrtko Ursulin <tursulin@...lia.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 kernel-dev@...lia.com, Maíra Canal <mcanal@...lia.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH 1/2] numa: Add simple generic NUMA emulation


Hi Greg,

On 26/06/2024 08:38, Greg Kroah-Hartman wrote:
> On Tue, Jun 25, 2024 at 01:58:02PM +0100, Tvrtko Ursulin wrote:
>> From: Maíra Canal <mcanal@...lia.com>
>>
>> Add some common code for splitting the memory into N emulated NUMA memory
>> nodes.
>>
>> Individual architecture can then enable selecting this option and use the
>> existing numa=fake=<N> kernel argument to enable it.
>>
>> Memory is always split into equally sized chunks.
>>
>> Signed-off-by: Maíra Canal <mcanal@...lia.com>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
>> Co-developed-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: “Rafael J. Wysocki" <rafael@...nel.org>
>> ---
>>   drivers/base/Kconfig          |  7 ++++
>>   drivers/base/Makefile         |  1 +
>>   drivers/base/arch_numa.c      |  6 ++++
>>   drivers/base/numa_emulation.c | 67 +++++++++++++++++++++++++++++++++++
>>   drivers/base/numa_emulation.h | 21 +++++++++++
> 
> Why not just properly describe the numa topology in your bootloader or
> device tree and not need any such "fake" stuff at all?
> 
> Also, you are now asking me to maintain these new files, not something
> I'm comfortable doing at all sorry.

Mostly because ae3c107cd8be ("numa: Move numa implementation to common 
code") and existing common code in drivers/base/arch_numa.c it appeared 
it could be acceptable to add the simple NUMA emulation into the common 
code too. Then building upon the same concept as on x86 where no need 
for firmware changes is needed for experimenting with different 
configurations.

Would folding into arch_numa.c so no new files are added address your 
concern, or your main issue is the emulation in general?

 >> +	if (str_has_prefix(opt, "fake="))
 >> +		return numa_emu_cmdline(opt + 5);
 >
 > You did not document this at all :(

That was indeed an oversight. Just need to "copy with edits" some stuff 
from Documentation/arch/x86/x86_64/boot-options.rst.

Regards,

Tvrtko