linux-kernel - Re: [Xen-devel] [PATCH 0/1] drm/xen-zcopy: Add Xen zero-copy helper DRM driver

Open Source and information security mailing list archives

Message-ID: <18ab5f76-00b0-42a0-fcb8-e0cbf4cdd527@gmail.com>
Date:   Tue, 24 Apr 2018 14:59:39 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Wei Liu <wei.liu2@...rix.com>, jgross@...e.com,
        Artem Mygaiev <Artem_Mygaiev@...m.com>,
        Dongwon Kim <dongwon.kim@...el.com>, konrad.wilk@...cle.com,
        airlied@...ux.ie, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        "Potrola, MateuszX" <mateuszx.potrola@...el.com>,
        daniel.vetter@...el.com, xen-devel@...ts.xenproject.org,
        boris.ostrovsky@...cle.com,
        Roger Pau Monné <roger.pau@...rix.com>
Cc:     "Oleksandr_Andrushchenko@...m.com" <Oleksandr_Andrushchenko@...m.com>
Subject: Re: [Xen-devel] [PATCH 0/1] drm/xen-zcopy: Add Xen zero-copy helper
 DRM driver

On 04/24/2018 02:54 PM, Daniel Vetter wrote:
> On Mon, Apr 23, 2018 at 03:10:35PM +0300, Oleksandr Andrushchenko wrote:
>> On 04/23/2018 02:52 PM, Wei Liu wrote:
>>> On Fri, Apr 20, 2018 at 02:25:20PM +0300, Oleksandr Andrushchenko wrote:
>>>>>>       the gntdev.
>>>>>>
>>>>>> I think this is generic enough that it could be implemented by a
>>>>>> device not tied to Xen. AFAICT the hyper_dma guys also wanted
>>>>>> something similar to this.
>>>>> You can't just wrap random userspace memory into a dma-buf. We've just had
>>>>> this discussion with kvm/qemu folks, who proposed just that, and after a
>>>>> bit of discussion they'll now try to have a driver which just wraps a
>>>>> memfd into a dma-buf.
>>>> So, we have to decide either we introduce a new driver
>>>> (say, under drivers/xen/xen-dma-buf) or extend the existing
>>>> gntdev/balloon to support dma-buf use-cases.
>>>>
>>>> Can anybody from Xen community express their preference here?
>>>>
>>> Oleksandr talked to me on IRC about this, he said a few IOCTLs need to
>>> be added to either existing drivers or a new driver.
>>>
>>> I went through this thread twice and skimmed through the relevant
>>> documents, but I couldn't see any obvious pros and cons for either
>>> approach. So I don't really have an opinion on this.
>>>
>>> But, assuming if implemented in existing drivers, those IOCTLs need to
>>> be added to different drivers, which means userspace program needs to
>>> write more code and get more handles, it would be slightly better to
>>> implement a new driver from that perspective.
>> If gntdev/balloon extension is still considered:
>>
>> All the IOCTLs will be in gntdev driver (in current xen-zcopy terminology):
I was lazy to change dumb to dma-buf, so put this notice ;)
>>   - DRM_ICOTL_XEN_ZCOPY_DUMB_FROM_REFS
>>   - DRM_IOCTL_XEN_ZCOPY_DUMB_TO_REFS
>>   - DRM_IOCTL_XEN_ZCOPY_DUMB_WAIT_FREE
> s/DUMB/DMA_BUF/ please. This is generic dma-buf, it has nothing to do with
> the dumb scanout buffer support in the drm/gfx subsystem. This here can be
> used for any zcopy sharing among guests (as long as your endpoints
> understands dma-buf, which most relevant drivers do).
Of course, please see above
> -Daniel
>
>> Balloon driver extension, which is needed for contiguous/DMA
>> buffers, will be to provide new *kernel API*, no UAPI is needed.
>>
>>> Wei.
>> Thank you,
>> Oleksandr
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives