From: Tyler Hicks <code@tyhicks.com>
To: Will Deacon <will@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>,
Robin Murphy <robin.murphy@arm.com>,
Jerry Snitselaar <jsnitsel@redhat.com>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, Dexuan Cui <decui@microsoft.com>,
Easwar Hariharan <eahariha@linux.microsoft.com>
Subject: Re: Why is the ARM SMMU v1/v2 put into bypass mode on kexec?
Date: Fri, 22 Mar 2024 14:52:52 -0500 [thread overview]
Message-ID: <Zf3hlOcYd7LB6Xvj@sequoia> (raw)
In-Reply-To: <20240322155529.GE5634@willie-the-truck>
On 2024-03-22 15:55:29, Will Deacon wrote:
> Hey Jason,
>
> On Tue, Mar 19, 2024 at 02:50:07PM -0300, Jason Gunthorpe wrote:
> > On Tue, Mar 19, 2024 at 03:47:56PM +0000, Will Deacon wrote:
> >
> > > Right, it's hard to win if DMA-active devices weren't quiesced properly
> > > by the outgoing kernel. Either the SMMU was left in abort (leading to the
> > > problems you list above) or the SMMU is left in bypass (leading to possible
> > > data corruption). Which is better?
> >
> > For whatever reason (and I really don't like this design) alot of work
> > was done on x86 so that device continues to work as-was right up until
> > the crash kernel does the first DMA operation. Including having the
> > crash kernel non disruptively inherit and retain the IOMMU
> > configuration. (eg see translation_pre_enabled() stuff in intel
> > driver)
>
> Right, I'm also not thrilled about trying to implement that :)
> What we have at the moment seems to be good enough to avoid folks
> complaining about it.
>
> For the case Tyler is reporting, though, I _think_ it's just a standard
> kexec() rather than a crashkernel.
That's correct.
Tyler
_______________________________________________
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:[~2024-03-22 19:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-14 7:49 Why is the ARM SMMU v1/v2 put into bypass mode on kexec? Tyler Hicks
2024-03-14 19:06 ` Tyler Hicks
2024-03-19 12:57 ` Robin Murphy
2024-03-19 15:47 ` Will Deacon
2024-03-19 17:50 ` Jason Gunthorpe
2024-03-22 15:55 ` Will Deacon
2024-03-22 19:52 ` Tyler Hicks [this message]
2024-03-19 18:17 ` Robin Murphy
2024-03-22 15:51 ` Will Deacon
2024-04-02 16:32 ` Robin Murphy
2024-03-19 19:14 ` Tyler Hicks
2024-03-22 16:06 ` Will Deacon
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=Zf3hlOcYd7LB6Xvj@sequoia \
--to=code@tyhicks.com \
--cc=decui@microsoft.com \
--cc=eahariha@linux.microsoft.com \
--cc=iommu@lists.linux.dev \
--cc=jgg@ziepe.ca \
--cc=jsnitsel@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=robin.murphy@arm.com \
--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).