linux-ext4 - Re: [PATCH v1 03/14] mm: add iomem vma selection for memory migration

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Date:   Wed, 25 Aug 2021 13:24:22 -0500
From:   "Sierra Guiza, Alejandro (Alex)" <alex.sierra@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     akpm@...ux-foundation.org, Felix.Kuehling@....com,
        linux-mm@...ck.org, rcampbell@...dia.com,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        jgg@...dia.com, jglisse@...hat.com
Subject: Re: [PATCH v1 03/14] mm: add iomem vma selection for memory migration


On 8/25/2021 2:46 AM, Christoph Hellwig wrote:
> On Tue, Aug 24, 2021 at 10:48:17PM -0500, Alex Sierra wrote:
>>   		} else {
>> -			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
>> +			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM) &&
>> +			    !(migrate->flags & MIGRATE_VMA_SELECT_IOMEM))
>>   				goto next;
>>   			pfn = pte_pfn(pte);
>>   			if (is_zero_pfn(pfn)) {
> .. also how is this going to work for the device public memory?  That
> should be pte_special() an thus fail vm_normal_page.
Perhaps we're missing something, as we're not doing any special marking 
for the device public pfn/entries.
pfn_valid return true, pte_special return false and pfn_t_devmap return 
false on these pages. Same as system pages.
That's the reason vm_normal_page returns the page correctly through 
pfn_to_page helper.

Regards,
Alex S.