Re: [PATCH V6 0/7] ACPI: Support Generic Initiator proximity domains

From: Brice Goglin <brice.goglin@gmail.com>
To: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: linux-mm@kvack.org, linux-acpi@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, x86@kernel.org,
	Keith Busch <kbusch@kernel.org>,
	jglisse@redhat.com, "Rafael J . Wysocki" <rjw@rjwysocki.net>,
	linuxarm@huawei.com, Andrew Morton <akpm@linux-foundation.org>,
	Dan Williams <dan.j.williams@intel.com>,
	Tao Xu <tao3.xu@intel.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Hanjun Guo <guohanjun@huawei.com>,
	Sudeep Holla <sudeep.holla@arm.com>
Subject: Re: [PATCH V6 0/7] ACPI: Support Generic Initiator proximity domains
Date: Fri, 20 Dec 2019 22:40:18 +0100	[thread overview]
Message-ID: <1867024e-b0c4-c291-7190-262cc4b297a8@gmail.com> (raw)
In-Reply-To: <20191218145041.00005a11@Huawei.com>

Le 18/12/2019 à 15:50, Jonathan Cameron a écrit :
> On Wed, 18 Dec 2019 12:32:06 +0100
> Brice Goglin <brice.goglin@gmail.com> wrote:
>
>> Le 16/12/2019 à 16:38, Jonathan Cameron a écrit :
>>> Introduces a new type of NUMA node for cases where we want to represent
>>> the access characteristics of a non CPU initiator of memory requests,
>>> as these differ from all those for existing nodes containing CPUs and/or
>>> memory.
>>>
>>> These Generic Initiators are presented by the node access0 class in
>>> sysfs in the same way as a CPU.   It seems likely that there will be
>>> usecases in which the best 'CPU' is desired and Generic Initiators
>>> should be ignored.  The final few patches in this series introduced
>>> access1 which is a new performance class in the sysfs node description
>>> which presents only CPU to memory relationships.  Test cases for this
>>> are described below.  
>>
>> Hello Jonathan
>>
>> If I want to test this with a fake GI, what are the minimal set of
>> changes I should put in my ACPI tables? Can I just specify a dummy GI in
>> SRAT? What handle should I use there?
> Exactly that for a dummy GI.  Also extend HMAT and SLIT for the extra
> proximity domain / initiator.

I couldn't get this to work (your patches on top of 5.5-rc2). I added
the GI in SRAT, and extended HMAT and SLIT accordingly.

I don't know if that's expected but I get an additional node in sysfs,
with 0kB memory.

However the HMAT table gets ignored because find_mem_target() fails in
hmat_parse_proximity_domain(). The target should have been allocated in
alloc_memory_target() which is called in srat_parse_mem_affinity(), but
it seems to me that this function isn't called for GI nodes. Or should
SRAT also contain a normal Memory node with same PM as the GI?

Brice