From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: "Christian König" <christian.koenig@amd.com>
Cc: Lei Liu <liulei.rjpt@vivo.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Benjamin Gaignard <benjamin.gaignard@collabora.com>,
Brian Starkey <Brian.Starkey@arm.com>,
John Stultz <jstultz@google.com>,
"T.J. Mercier" <tjmercier@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Muhammad Usama Anjum <usama.anjum@collabora.com>,
Andrei Vagin <avagin@google.com>,
Ryan Roberts <ryan.roberts@arm.com>,
Kefeng Wang <wangkefeng.wang@huawei.com>,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Daniel Vetter <daniel@ffwll.ch>,
"Vetter, Daniel" <daniel.vetter@intel.com>,
opensource.kernel@vivo.com
Subject: Re: [PATCH 0/2] Support direct I/O read and write for memory allocated by dmabuf
Date: Mon, 15 Jul 2024 10:52:23 +0200 [thread overview]
Message-ID: <ZpTjR-7dabdyREXS@phenom.ffwll.local> (raw)
In-Reply-To: <5e5ee5d3-8a57-478a-9ce7-b40cab60b67d@amd.com>
On Wed, Jul 10, 2024 at 04:14:18PM +0200, Christian König wrote:
> Am 10.07.24 um 15:57 schrieb Lei Liu:
> > Use vm_insert_page to establish a mapping for the memory allocated
> > by dmabuf, thus supporting direct I/O read and write; and fix the
> > issue of incorrect memory statistics after mapping dmabuf memory.
>
> Well big NAK to that! Direct I/O is intentionally disabled on DMA-bufs.
>
> We already discussed enforcing that in the DMA-buf framework and this patch
> probably means that we should really do that.
Last time I looked dma_mmap doesn't guarantee that the vma end sup with
VM_SPECIAL, and that's pretty much the only reason why we can't enforce
this. But we might be able to enforce this at least on some architectures,
I didn't check for that ... if at least x86-64 and arm64 could have the
check, that would be great. So might be worth it to re-audit this all.
I think all other dma-buf exporters/allocators do only create VM_SPECIAL
vmas.
-Sima
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
next prev parent reply other threads:[~2024-07-15 8:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-10 13:57 Lei Liu
2024-07-10 13:57 ` [PATCH 1/2] mm: dmabuf_direct_io: Support direct_io " Lei Liu
2024-07-10 14:14 ` [PATCH 0/2] Support direct I/O read and write " Christian König
2024-07-10 14:35 ` Lei Liu
2024-07-10 14:48 ` Christian König
2024-07-10 15:06 ` Lei Liu
2024-07-10 16:34 ` T.J. Mercier
2024-07-11 14:25 ` Christian König
2024-07-15 9:07 ` Lei Liu
2024-07-15 8:52 ` Daniel Vetter [this message]
2024-07-10 14:09 Lei Liu
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