linux-kernel - Re: [PATCH 2/2] xen: don't use page->lru for ZONE

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Date:   Tue, 8 Dec 2020 07:45:00 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Jason Andryuk <jandryuk@...il.com>
Cc:     xen-devel <xen-devel@...ts.xenproject.org>,
        open list <linux-kernel@...r.kernel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>
Subject: Re: [PATCH 2/2] xen: don't use page->lru for ZONE_DEVICE memory

On 07.12.20 21:48, Jason Andryuk wrote:
> On Mon, Dec 7, 2020 at 8:30 AM Juergen Gross <jgross@...e.com> wrote:
>>
>> Commit 9e2369c06c8a18 ("xen: add helpers to allocate unpopulated
>> memory") introduced usage of ZONE_DEVICE memory for foreign memory
>> mappings.
>>
>> Unfortunately this collides with using page->lru for Xen backend
>> private page caches.
>>
>> Fix that by using page->zone_device_data instead.
>>
>> Fixes: 9e2369c06c8a18 ("xen: add helpers to allocate unpopulated memory")
>> Signed-off-by: Juergen Gross <jgross@...e.com>
> 
> Would it make sense to add BUG_ON(is_zone_device_page(page)) and the
> opposite as appropriate to cache_enq?

No, I don't think so. At least in the CONFIG_ZONE_DEVICE case the
initial list in a PV dom0 is populated from extra memory (basically
the same, but not marked as zone device memory explicitly).

Juergen

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