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From:   "Huang, Ying" <ying.huang@intel.com>
To:     "Verma, Vishal L" <vishal.l.verma@intel.com>
Cc:     "david@redhat.com" <david@redhat.com>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "osalvador@suse.de" <osalvador@suse.de>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Williams, Dan J" <dan.j.williams@intel.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "Jonathan.Cameron@Huawei.com" <Jonathan.Cameron@Huawei.com>,
        "nvdimm@lists.linux.dev" <nvdimm@lists.linux.dev>,
        "aneesh.kumar@linux.ibm.com" <aneesh.kumar@linux.ibm.com>,
        "jmoyer@redhat.com" <jmoyer@redhat.com>,
        "linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mike Rapoport <rppt@kernel.org>,
        Bernhard Walle <bernhard.walle@gmx.de>
Subject: Re: [PATCH v2 2/3] mm/memory_hotplug: split memmap_on_memory
 requests across memblocks
References: <20230720-vv-kmem_memmap-v2-0-88bdaab34993@intel.com>
        <20230720-vv-kmem_memmap-v2-2-88bdaab34993@intel.com>
        <87wmyp26sw.fsf@yhuang6-desk2.ccr.corp.intel.com>
        <abe41c22f72ad600541c6f2b199180b1cbcbb780.camel@intel.com>
Date:   Mon, 14 Aug 2023 14:45:11 +0800
In-Reply-To: <abe41c22f72ad600541c6f2b199180b1cbcbb780.camel@intel.com>
        (Vishal L. Verma's message of "Wed, 2 Aug 2023 14:08:20 +0800")
Message-ID: <87jzty9l6w.fsf@yhuang6-desk2.ccr.corp.intel.com>
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"Verma, Vishal L" <vishal.l.verma@intel.com> writes:

> On Mon, 2023-07-24 at 13:54 +0800, Huang, Ying wrote:
>> Vishal Verma <vishal.l.verma@intel.com> writes:
>>
>> >
>> > @@ -2035,12 +2056,38 @@ void try_offline_node(int nid)
>> >  }
>> >  EXPORT_SYMBOL(try_offline_node);
>> >
>> > -static int __ref try_remove_memory(u64 start, u64 size)
>> > +static void __ref __try_remove_memory(int nid, u64 start, u64 size,
>> > +                                    struct vmem_altmap *altmap)
>> >  {
>> > -       struct vmem_altmap mhp_altmap = {};
>> > -       struct vmem_altmap *altmap = NULL;
>> > -       unsigned long nr_vmemmap_pages;
>> > -       int rc = 0, nid = NUMA_NO_NODE;
>> > +       /* remove memmap entry */
>> > +       firmware_map_remove(start, start + size, "System RAM");
>>
>> If mhp_supports_memmap_on_memory(), we will call
>> firmware_map_add_hotplug() for whole range.  But here we may call
>> firmware_map_remove() for part of range.  Is it OK?
>>
>
> Good point, this is a discrepancy in the add vs remove path. Can the
> firmware memmap entries be moved up a bit in the add path, and is it
> okay to create these for each memblock? Or should these be for the
> whole range? I'm not familiar with the implications. (I've left it as
> is for v3 for now, but depending on the direction I can update in a
> future rev).

Cced more firmware map developers and maintainers.

Per my understanding, we should create one firmware memmap entry for
each memblock.

--
Best Regards,
Huang, Ying