linux-kernel - Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem rework

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Message-ID: <20190521103214.GB1973@lst.de>
Date:   Tue, 21 May 2019 12:32:14 +0200
From:   "hch@....de" <hch@....de>
To:     Fredrik Noring <noring@...rew.org>
Cc:     Laurentiu Tudor <laurentiu.tudor@....com>,
        Robin Murphy <robin.murphy@....com>, "hch@....de" <hch@....de>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "marex@...x.de" <marex@...x.de>,
        "JuergenUrban@....de" <JuergenUrban@....de>,
        Leo Li <leoyang.li@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 0/3] prerequisites for device reserved local mem
 rework

On Mon, May 20, 2019 at 05:41:56PM +0200, Fredrik Noring wrote:
> 2. A device address is supplied as phys_addr_t phys to gen_pool_add_virt().
>    This seems to work in this particular DMA application, but there will be
>    problems if someone does phys_to_virt() or suchlike. Can this be improved
>    or clearly explained? gen_pool_virt_to_phys() searches in address ranges,
>    for example, so it appears the implementation uses phys quite carefully.

Well, it is a physical address, but not one that has a kernel mapping.
So phys_addr_t seems right here, but an additional comment explaining it
is not in the kernel mapping never hurts.