From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: Jason Gunthorpe <jgg@ziepe.ca>, Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Christian König" <christian.koenig@amd.com>,
"DRI Development" <dri-devel@lists.freedesktop.org>,
"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"Suren Baghdasaryan" <surenb@google.com>,
"Matthew Wilcox" <willy@infradead.org>,
"John Stultz" <john.stultz@linaro.org>,
"Daniel Vetter" <daniel.vetter@intel.com>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org
Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-buf: Require VM_PFNMAP vma for mmap
Date: Wed, 23 Nov 2022 13:49:41 +0100 [thread overview]
Message-ID: <f8f844a5-0910-d19a-5aea-df7a1d83b1d3@gmail.com> (raw)
In-Reply-To: <Y34WI9SZdiH/p1tA@ziepe.ca>
Am 23.11.22 um 13:46 schrieb Jason Gunthorpe:
> On Wed, Nov 23, 2022 at 11:06:55AM +0100, Daniel Vetter wrote:
>
>>> Maybe a GFP flag to set the page reference count to zero or something
>>> like this?
>> Hm yeah that might work. I'm not sure what it will all break though?
>> And we'd need to make sure that underflowing the page refcount dies in
>> a backtrace.
> Mucking with the refcount like this to protect against crazy out of
> tree drives seems horrible..
Well not only out of tree drivers. The intree KVM got that horrible
wrong as well, those where the latest guys complaining about it.
>
> The WARN_ON(pag_count(p) != 1) seems like a reasonable thing to do
> though, though you must combine this with the special PTE flag..
That's not sufficient. The pages are released much later than things
actually go wrong. In most cases this WARN_ON here won't hit.
Christian.
>
> Jason
next prev parent reply other threads:[~2022-11-23 13:06 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-22 17:08 [PATCH] dma-buf: Require VM_PFNMAP vma for mmap Daniel Vetter
2022-11-22 18:03 ` Jason Gunthorpe
2022-11-22 18:08 ` Daniel Vetter
2022-11-22 18:50 ` Jason Gunthorpe
2022-11-22 19:29 ` Daniel Vetter
2022-11-22 19:34 ` Jason Gunthorpe
2022-11-22 19:50 ` Daniel Vetter
2022-11-23 9:06 ` Christian König
2022-11-23 9:30 ` Daniel Vetter
2022-11-23 9:39 ` [Linaro-mm-sig] " Christian König
2022-11-23 10:06 ` Daniel Vetter
2022-11-23 12:46 ` Jason Gunthorpe
2022-11-23 12:49 ` Christian König [this message]
2022-11-23 12:53 ` Jason Gunthorpe
2022-11-23 13:12 ` Christian König
2022-11-23 13:28 ` Jason Gunthorpe
2022-11-23 14:28 ` Daniel Vetter
2022-11-23 15:04 ` Jason Gunthorpe
2022-11-23 16:22 ` Daniel Vetter
2022-11-23 14:34 ` Daniel Vetter
2022-11-23 15:08 ` Jason Gunthorpe
2022-11-23 15:15 ` Christian König
2022-11-23 16:26 ` Daniel Vetter
2022-11-23 16:26 ` Jason Gunthorpe
2022-11-23 8:07 ` Thomas Zimmermann
2022-11-23 9:33 ` Daniel Vetter
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