From: Jason Gunthorpe <jgg@ziepe.ca>
To: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>,
nicolinc@nvidia.com, james.morse@arm.com, robin.murphy@arm.com,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [v3 PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for 32-bit sid size
Date: Tue, 8 Oct 2024 12:15:06 -0300 [thread overview]
Message-ID: <20241008151506.GC762027@ziepe.ca> (raw)
In-Reply-To: <20241008133458.GA10474@willie-the-truck>
On Tue, Oct 08, 2024 at 02:34:58PM +0100, Will Deacon wrote:
> This all looks a bit messy to me. The architecture guarantees that
> 2-level stream tables are supported once we hit 7-bit SIDs and, although
> the driver relaxes this to > 8-bit SIDs, we'll never run into overflow
> problems in the linear table code above.
My original point was about the confidential compute position (sigh)
that the untrusted hypverisor should not corrupt the driver.
So your statement is architecturally true, but we never check that
IDR0_ST_LVL_2LVL is set if IDR1_SIDSIZE > 2**7, and so we can get into
this situation where the hypervisor could trigger some kind of bad
behavior.
> So I'm inclined to take Daniel's one-liner [1] which just chucks the
> 'ULL' suffix into the 2-level case. Otherwise, we're in a weird
I think you should take it and let better be for the CC crowd.
Jason
next prev parent reply other threads:[~2024-10-08 15:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-04 18:04 [v3 PATCH] iommu/arm-smmu-v3: Fix L1 stream table index calculation for 32-bit sid size Yang Shi
2024-10-04 21:14 ` Daniel Mentz
2024-10-04 21:47 ` Yang Shi
2024-10-05 1:03 ` Daniel Mentz
2024-10-05 1:53 ` Yang Shi
2024-10-07 16:36 ` Daniel Mentz
2024-10-07 17:49 ` Yang Shi
2024-10-07 17:50 ` Jason Gunthorpe
2024-10-07 18:43 ` Yang Shi
2024-10-08 13:34 ` Will Deacon
2024-10-08 15:15 ` Jason Gunthorpe [this message]
2024-10-08 17:04 ` Yang Shi
2024-10-08 17:41 ` Will Deacon
2024-10-08 17:42 ` 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=20241008151506.GC762027@ziepe.ca \
--to=jgg@ziepe.ca \
--cc=iommu@lists.linux.dev \
--cc=james.morse@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=nicolinc@nvidia.com \
--cc=robin.murphy@arm.com \
--cc=will@kernel.org \
--cc=yang@os.amperecomputing.com \
/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