From: Linus Torvalds <torvalds@linux-foundation.org>
To: Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Android Kernel Team <kernel-team@android.com>
Subject: Re: [GIT PULL] arm64 fix for 5.14
Date: Thu, 26 Aug 2021 11:41:34 -0700 [thread overview]
Message-ID: <CAHk-=wi8Wxazuq+E4_V0GG4eda0rNpZi76AYWQe7xfPZAAexAQ@mail.gmail.com> (raw)
In-Reply-To: <20210826131747.GE26318@willie-the-truck>
On Thu, Aug 26, 2021 at 6:17 AM Will Deacon <will@kernel.org> wrote:
>
> Please pull this single arm64 fix for 5.14.
Pulled.
But adding Christoph to the cc, since I do think the eventual fix
needs to be in the DMA mapping code:
> We received a report this week
> that the generic version of pfn_valid(), which we switched to this merge
> window in 16c9afc77660 ("arm64/mm: drop HAVE_ARCH_PFN_VALID"), interacts
> badly with dma_map_resource() due to the following check:
>
> /* Don't allow RAM to be mapped */
> if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
> return DMA_MAPPING_ERROR;
>
> Since the ongoing saga to determine the semantics of pfn_valid() is
> unlikely to be resolved this week (does it indicate valid memory, or
> just the presence of a struct page, or whether that struct page has been
> initialised?), just revert back to our old version of pfn_valid() for
> 5.14.
I think that's the right thing for now, but yeah, that condition for
WARN_ON_ONCE() seems very questionable.
"pfn_valid()" is more about whether you can do a "pfn_to_page()" lookup on it.
II get the feeling that the dma-mapping code should allow pages that
are PageReserved() to be mapped - they aren't "ram" in the kernel
sense.
Perhaps also make sure it's not the zero page (which is
PageReserved(), but most definitely RAM).
In a PC world that would be (for example) the legacy PCI space at
0xa0000-0xfffff, but I could easily imagine other platforms having
other situations.
Linus
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-08-26 18:44 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-26 13:17 [GIT PULL] arm64 fix for 5.14 Will Deacon
2021-08-26 18:41 ` Linus Torvalds [this message]
2021-08-27 7:40 ` Christoph Hellwig
2021-08-27 17:03 ` Linus Torvalds
2021-08-27 17:10 ` Christoph Hellwig
2021-08-27 17:16 ` Linus Torvalds
2021-08-31 13:31 ` Will Deacon
2021-08-31 19:16 ` David Hildenbrand
2021-08-31 16:56 ` Catalin Marinas
2021-08-26 18:52 ` pr-tracker-bot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAHk-=wi8Wxazuq+E4_V0GG4eda0rNpZi76AYWQe7xfPZAAexAQ@mail.gmail.com' \
--to=torvalds@linux-foundation.org \
--cc=catalin.marinas@arm.com \
--cc=hch@lst.de \
--cc=kernel-team@android.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).