Re: [PATCHv6 07/10] acpi/hmat: Register processor domain to its memory
From: Keith Busch
Date: Wed Feb 20 2019 - 17:44:23 EST
On Wed, Feb 20, 2019 at 11:21:45PM +0100, Rafael J. Wysocki wrote:
> On Wed, Feb 20, 2019 at 11:11 PM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> > 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?
> Maybe it would be better to make HMEM_REPORTING do "select ACPI_HMAT if ACPI".
> The mitigations could then do that too if they depend on HMAT and
> ACPI_HMAT need not be user-visible at all.
That sounds okay, though it would create unreachable code if !ACPI since
that's the only user for the new reporting interfaces.