Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM

From	Benjamin Herrenschmidt <benh@kernel.crashing.org>
Newsgroups	linux.kernel
Subject	Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM
Date	2017-06-15 00:10 +0200
Message-ID	<tSoEa-2rK-11@gated-at.bofh.it> (permalink)
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On Wed, 2017-06-14 at 14:58 -0700, Dave Hansen wrote:
> > > http://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
> > 
> > It doesn't interact with that. HMM-CDM is a set of helper that don't
> > do anything unless instructed so. So for device memory to be presented
> > as HMM-CDM you need to hotplug it as ZONE_DEVICE(DEVICE_PUBLIC) which
> > can be done with the helper introduced in patch 2 of this patchset.
> 
> I guess I'm asking whether we *should* instruct HMM-CDM to manage all
> coherent device memory.  If not, where do we draw the line for what we
> use HMM-CDM, and for what we use the core MM?

Well, if you want the features of HMM ... It basically boils down to
whether you have some kind of coherent processing unit close to that
memory and want to manage transparent migration of pages between system
and device memory, that sort of thing.

Cheers,
Ben.

Thread

[HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Jérôme Glisse <jglisse@redhat.com> - 2017-06-14 22:20 +0200
  Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Dave Hansen <dave.hansen@intel.com> - 2017-06-14 23:30 +0200
    Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Jerome Glisse <jglisse@redhat.com> - 2017-06-14 23:40 +0200
      Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Dave Hansen <dave.hansen@intel.com> - 2017-06-15 00:00 +0200
        Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-06-15 00:10 +0200
        Re: [HMM-CDM 0/5] Cache coherent device memory (CDM) with HMM Balbir Singh <bsingharora@gmail.com> - 2017-06-15 01:50 +0200

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