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Subject: Re: [PATCH v3 3/5] mm/migrate.c: fix potential indeterminate pte
 entry in migrate_vma_insert_page()
To:     Miaohe Lin <linmiaohe@huawei.com>, akpm@linux-foundation.org
Cc:     jglisse@redhat.com, shy828301@gmail.com, aquini@redhat.com,
        apopple@nvidia.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
References: <20210325131524.48181-1-linmiaohe@huawei.com>
 <20210325131524.48181-4-linmiaohe@huawei.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <b0cdddeb-c790-082b-810a-77c79de48557@redhat.com>
Date:   Thu, 25 Mar 2021 14:26:35 +0100
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On 25.03.21 14:15, Miaohe Lin wrote:
> If the zone device page does not belong to un-addressable device memory,
> the variable entry will be uninitialized and lead to indeterminate pte
> entry ultimately. Fix this unexpected case and warn about it.
> 
> Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>   mm/migrate.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/mm/migrate.c b/mm/migrate.c
> index dacbdc9710ac..87bbad578127 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2968,6 +2968,13 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
>   
>   			swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
>   			entry = swp_entry_to_pte(swp_entry);
> +		} else {
> +			/*
> +			 * For now we only support migrating to un-addressable
> +			 * device memory.
> +			 */
> +			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
> +			goto abort;
>   		}
>   	} else {
>   		entry = mk_pte(page, vma->vm_page_prot);
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb