From: Linus Torvalds <torvalds@linux-foundation.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: "Toke Høiland-Jørgensen" <toke@toke.dk>,
"Christoph Hellwig" <hch@lst.de>,
"Halil Pasic" <pasic@linux.ibm.com>,
"Oleksandr Natalenko" <oleksandr@natalenko.name>,
"Marek Szyprowski" <m.szyprowski@samsung.com>,
"Kalle Valo" <kvalo@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"Paolo Abeni" <pabeni@redhat.com>,
"Olha Cherevyk" <olha.cherevyk@gmail.com>,
iommu <iommu@lists.linux-foundation.org>,
linux-wireless <linux-wireless@vger.kernel.org>,
Netdev <netdev@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
stable <stable@vger.kernel.org>
Subject: Re: [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break ath9k-based AP
Date: Fri, 25 Mar 2022 11:46:09 -0700 [thread overview]
Message-ID: <CAHk-=wgKF5GfLXyVGDQDifh0MpMccDdmBvJBG3dt2+idCa5DzQ@mail.gmail.com> (raw)
In-Reply-To: <e077b229-c92b-c9a6-3581-61329c4b4a4b@arm.com>
On Fri, Mar 25, 2022 at 11:42 AM Robin Murphy <robin.murphy@arm.com> wrote:
>
> Note that the current code is already a violation of the DMA
> API (because the device keeps writing even when it doesn't have
> ownership), so there's not a very strong argument in that regard.
See my other email. I actually think that the ath9k code is 100%
correct, adn it's the dma-mapping code that is in violation of the
rules.
And a big part of the problem - I think - is that the rules are so
badly documented and not explicitly listed.
I think my list of three different sync cases (not just two! It's not
just about whether to sync for the CPU or the device, it's also about
what direction the data itself is taking) is correct.
But maybe I'm wrong.
I really want people to think about this, because right now my gut
feel is that commit aa6f8dcbab47 was just absolutely incorrect.
Linus
next prev parent reply other threads:[~2022-03-25 19:42 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 7:19 [REGRESSION] Recent swiotlb DMA_FROM_DEVICE fixes break ath9k-based AP Oleksandr Natalenko
2022-03-23 7:28 ` Kalle Valo
2022-03-23 17:27 ` Linus Torvalds
2022-03-23 19:06 ` Robin Murphy
2022-03-23 19:16 ` Linus Torvalds
2022-03-23 20:54 ` Robin Murphy
2022-03-24 5:57 ` Christoph Hellwig
2022-03-24 10:25 ` Oleksandr Natalenko
2022-03-24 11:05 ` Robin Murphy
2022-03-24 14:27 ` Toke Høiland-Jørgensen
2022-03-24 16:29 ` Maxime Bizon
2022-03-24 16:31 ` Christoph Hellwig
2022-03-24 16:52 ` Robin Murphy
2022-03-24 17:07 ` Toke Høiland-Jørgensen
2022-03-24 19:26 ` Linus Torvalds
2022-03-24 21:14 ` Toke Høiland-Jørgensen
2022-03-25 10:25 ` Maxime Bizon
2022-03-25 11:27 ` Robin Murphy
2022-03-25 23:38 ` Halil Pasic
2022-03-26 16:05 ` Toke Høiland-Jørgensen
2022-03-26 18:38 ` Linus Torvalds
2022-03-26 22:38 ` David Laight
2022-03-26 22:41 ` Linus Torvalds
2022-03-25 16:25 ` Toke Høiland-Jørgensen
2022-03-25 16:45 ` Robin Murphy
2022-03-25 18:13 ` Toke Høiland-Jørgensen
2022-03-25 18:30 ` Linus Torvalds
2022-03-25 19:14 ` Robin Murphy
2022-03-25 19:21 ` Linus Torvalds
2022-03-25 19:26 ` Oleksandr Natalenko
2022-03-25 19:27 ` Linus Torvalds
2022-03-25 19:35 ` Oleksandr Natalenko
2022-03-25 20:37 ` Johannes Berg
2022-03-25 20:47 ` Linus Torvalds
2022-03-25 21:13 ` Johannes Berg
2022-03-25 21:40 ` David Laight
2022-03-25 21:56 ` Linus Torvalds
2022-03-25 22:41 ` David Laight
2022-03-27 3:15 ` Halil Pasic
2022-03-28 9:48 ` Johannes Berg
2022-03-28 9:50 ` Johannes Berg
2022-03-28 9:57 ` Johannes Berg
2022-03-27 3:48 ` Halil Pasic
2022-03-27 5:06 ` Linus Torvalds
2022-03-27 5:21 ` Linus Torvalds
2022-03-27 15:24 ` David Laight
2022-03-27 19:23 ` Linus Torvalds
2022-03-27 20:04 ` Linus Torvalds
2022-03-27 23:52 ` Halil Pasic
2022-03-28 0:30 ` Linus Torvalds
2022-03-28 12:02 ` Halil Pasic
2022-03-27 23:37 ` Halil Pasic
2022-03-28 0:37 ` Linus Torvalds
2022-03-25 7:12 ` Oleksandr Natalenko
2022-03-25 9:21 ` Thorsten Leemhuis
2022-03-24 18:31 ` Halil Pasic
2022-03-25 16:31 ` Christoph Hellwig
2022-03-24 18:02 ` Halil Pasic
2022-03-25 15:25 ` Halil Pasic
2022-03-25 16:23 ` Robin Murphy
2022-03-25 16:32 ` Christoph Hellwig
2022-03-25 18:15 ` Toke Høiland-Jørgensen
2022-03-25 18:42 ` Robin Murphy
2022-03-25 18:46 ` Linus Torvalds [this message]
2022-03-28 6:37 ` Christoph Hellwig
2022-03-28 8:15 ` David Laight
2022-03-30 12:11 ` Halil Pasic
2022-03-24 8:55 ` Oleksandr Natalenko
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