linux-kernel - Re: [PATCH] mm/device-public-memory: Enable move

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Date:   Fri, 22 Sep 2017 16:01:13 -0500
From:   Reza Arbab <arbab@...ux.vnet.ibm.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...e.com>, Jan Kara <jack@...e.cz>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Matthew Wilcox <willy@...ux.intel.com>,
        Hugh Dickins <hughd@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        James Morse <james.morse@....com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Minchan Kim <minchan@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Will Deacon <will.deacon@....com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/device-public-memory: Enable move_pages() to stat
 device memory

On Fri, Sep 22, 2017 at 08:31:57PM +0000, Reza Arbab wrote:
>On Fri, Sep 22, 2017 at 08:13:56PM +0000, Reza Arbab wrote:
>>The move_pages() syscall can be used to find the numa node where a page
>>currently resides. This is not working for device public memory pages,
>>which erroneously report -EFAULT (unmapped or zero page).
>
>Argh. Please disregard this patch.
>
>My test setup has a chunk of system memory carved out as pretend 
>device public memory, to experiment with. Of course the real thing has 
>no numa node!

On third thought, yes it does! 

static int hmm_devmem_pages_create(struct hmm_devmem *devmem)
{
	:
	nid = dev_to_node(device);
	if (nid < 0)
		nid = numa_mem_id();
	:
	if (devmem->pagemap.type == MEMORY_DEVICE_PUBLIC)
		ret = arch_add_memory(nid, align_start, align_size, false);
	:
}

So now I think the patch may be right after all. Please un-disregard it.  
Regard it? Whatever.

-- 
Reza Arbab