linux-kernel - Re: [PATCH v3 2/3] mm/hmm: allow snapshot of the special zero page

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Message-ID: <20191029172729.GQ22766@mellanox.com>
Date:   Tue, 29 Oct 2019 17:27:35 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Ralph Campbell <rcampbell@...dia.com>
CC:     Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Christoph Hellwig <hch@....de>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] mm/hmm: allow snapshot of the special zero page

On Wed, Oct 23, 2019 at 12:55:14PM -0700, Ralph Campbell wrote:
> If a device driver like nouveau tries to use hmm_range_fault() to access
> the special shared zero page in system memory, hmm_range_fault() will
> return -EFAULT and kill the process.
> Allow hmm_range_fault() to return success (0) when the CPU pagetable
> entry points to the special shared zero page.
> page_to_pfn() and pfn_to_page() are defined on the zero page so just
> handle it like any other page.
> 
> Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
> Cc: Christoph Hellwig <hch@....de>
> Cc: "Jérôme Glisse" <jglisse@...hat.com>
> Cc: Jason Gunthorpe <jgg@...lanox.com>
> ---
>  mm/hmm.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)

Applied to hmm.git

Thanks,
Jason