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From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: Rob Clark <robdclark@gmail.com>
Cc: "Christian König" <christian.koenig@amd.com>,
	dri-devel@lists.freedesktop.org,
	"Daniel Vetter" <daniel@ffwll.ch>,
	freedreno@lists.freedesktop.org,
	"Rob Clark" <robdclark@chromium.org>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Jérôme Pouiller" <jerome.pouiller@silabs.com>,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>,
	"moderated list:DMA BUFFER SHARING FRAMEWORK"
	<linaro-mm-sig@lists.linaro.org>,
	"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [Linaro-mm-sig] [PATCH 1/3] dma-buf: Add ioctl to query mmap info
Date: Sun, 7 Aug 2022 20:05:15 +0200	[thread overview]
Message-ID: <e2423bd7-ef73-8d43-c661-a19c80ad1a26@gmail.com> (raw)
In-Reply-To: <CAF6AEGv9H+fSFKPNqwPxYUjkgj05AimpXbp-p_JL8nKLnzON=w@mail.gmail.com>

Am 07.08.22 um 19:56 schrieb Rob Clark:
> On Sun, Aug 7, 2022 at 10:38 AM Christian König
> <ckoenig.leichtzumerken@gmail.com> wrote:
>> [SNIP]
>> And exactly that was declared completely illegal the last time it came
>> up on the mailing list.
>>
>> Daniel implemented a whole bunch of patches into the DMA-buf layer to
>> make it impossible for KVM to do this.
> This issue isn't really with KVM, it is not making any CPU mappings
> itself.  KVM is just making the pages available to the guest.

Well I can only repeat myself: This is strictly illegal.

Please try this approach with CONFIG_DMABUF_DEBUG set. I'm pretty sure 
you will immediately run into a crash.

See this here as well 
https://elixir.bootlin.com/linux/v5.19/source/drivers/dma-buf/dma-buf.c#L653

Daniel intentionally added code to mangle the page pointers to make it 
impossible for KVM to do this.

If the virtio/virtgpu UAPI was build around the idea that this is 
possible then it is most likely fundamental broken.

Regards,
Christian.

  reply	other threads:[~2022-08-07 18:05 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-29 17:07 [PATCH 0/3] dma-buf: map-info support Rob Clark
2022-07-29 17:07 ` [PATCH 1/3] dma-buf: Add ioctl to query mmap info Rob Clark
2022-07-29 21:27   ` kernel test robot
2022-07-30  2:42   ` kernel test robot
2022-07-30  6:12   ` kernel test robot
2022-07-30 23:01   ` kernel test robot
2022-08-07 16:09   ` [Linaro-mm-sig] " Christian König
2022-08-07 17:02     ` Rob Clark
2022-08-07 17:14       ` Christian König
2022-08-07 17:35         ` Rob Clark
2022-08-07 17:38           ` Christian König
2022-08-07 17:56             ` Rob Clark
2022-08-07 18:05               ` Christian König [this message]
2022-08-07 19:10                 ` Rob Clark
2022-08-08 11:22                   ` Christian König
2022-08-08 13:26                     ` Rob Clark
2022-08-08 14:56                       ` Christian König
2022-08-08 16:29                         ` Rob Clark
2022-08-07 20:25   ` [Freedreno] " Akhil P Oommen
2022-08-08 13:04     ` Rob Clark
2022-07-29 17:07 ` [PATCH 2/3] drm/prime: Wire up mmap_info support Rob Clark
2022-07-29 17:07 ` [PATCH 3/3] drm/msm/prime: Add " Rob Clark

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