linux-kernel - Re: [PATCHv6 07/10] acpi/hmat: Register processor domain to its memory

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Date:   Wed, 20 Feb 2019 14:11:10 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Keith Busch <keith.busch@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux API <linux-api@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCHv6 07/10] acpi/hmat: Register processor domain to its
 memory

On 2/20/19 2:02 PM, Rafael J. Wysocki wrote:
>> diff --git a/drivers/acpi/hmat/Kconfig b/drivers/acpi/hmat/Kconfig
>> index c9637e2e7514..08e972ead159 100644
>> --- a/drivers/acpi/hmat/Kconfig
>> +++ b/drivers/acpi/hmat/Kconfig
>> @@ -2,6 +2,7 @@
>>  config ACPI_HMAT
>>         bool "ACPI Heterogeneous Memory Attribute Table Support"
>>         depends on ACPI_NUMA
>> +       select HMEM_REPORTING
> If you want to do this here, I'm not sure that defining HMEM_REPORTING
> as a user-selectable option is a good idea.  In particular, I don't
> really think that setting ACPI_HMAT without it makes a lot of sense.
> Apart from this, the patch looks reasonable to me.

I guess the question is whether we would want to allow folks to consume
the HMAT inside the kernel while not reporting it out via
HMEM_REPORTING.  We have some in-kernel users of the HMAT lined up like
mitigations for memory-side caches.

It's certainly possible that folks would want to consume those
mitigations without anything in sysfs.  They might not even want or need
NUMA support itself, for instance.

So, what should we do?

config HMEM_REPORTING
	bool # no user-visible prompt
	default y if ACPI_HMAT

So folks can override in their .config, but they don't see a prompt?