From: Jason Gunthorpe <jgg@nvidia.com>
To: sonang patel <sonangp@nvidia.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
joro@8bytes.org, Robin Murphy <robin.murphy@arm.com>,
rafael@kernel.org, Danilo Krummrich <dakr@kernel.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
aneesh.kumar@kernel.org, Mark Rutland <mark.rutland@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Gavin Shan <gshan@redhat.com>, Vikram Sethi <vsethi@nvidia.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Shanker Donthineni <sdonthineni@nvidia.com>,
Mostafa Saleh <smostafa@google.com>,
rppt@kernel.org, Thomas Huth <thuth@redhat.com>,
Marc Zyngier <maz@kernel.org>,
Ryan Roberts <ryan.roberts@arm.com>,
kas@kernel.org, Kohei Enju <enju.kohei@fujitsu.com>,
Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>,
Ard Biesheuvel <ardb@kernel.org>,
James Morse <james.morse@arm.com>,
Steven Price <steven.price@arm.com>,
Sang-Heon Jeon <ekffu200098@gmail.com>,
Omar Sandoval <osandov@fb.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jinjie Ruan <ruanjinjie@huawei.com>,
Sam Edwards <cfsworks@gmail.com>,
Douglas Anderson <dianders@chromium.org>,
Florian Fainelli <florian.fainelli@broadcom.com>,
Chen-Yu Tsai <wenst@chromium.org>,
Huacai Chen <chenhuacai@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
Pranjal Shrivastava <praan@google.com>,
Ashish Mhetre <amhetre@nvidia.com>,
Shameer Kolothum <skolothumtho@nvidia.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
driver-core@lists.linux.dev, Ankit Agrawal <ankita@nvidia.com>
Subject: Re: [PATCH v1 6/8] iommu: Introduce TDISP T=0 state for confidential IOMMUs
Date: Thu, 17 Sep 2026 10:34:58 -0300 [thread overview]
Message-ID: <20260917133458.GB3968357@nvidia.com> (raw)
In-Reply-To: <aqvFcIkll6e2T6M7@sonangrm.nvidia.com>
On Thu, Sep 17, 2026 at 04:18:16PM +0530, sonang patel wrote:
> On Wed, 9 Sep 2026 20:32:49 -0700, Nicolin Chen wrote:
> > + * @tdisp_t1: device uses its confidential IOMMU's T=1 stream. A zero value
> > + * means T=0, where the T=1 stream remains blocked while the core
> > + * owns required DMA operations such as ATS.
>
> What happens when the TDI transitions to ERROR, and how does this bit
> signify it?
> A TDI can drop to ERROR asynchronously, and at that point the device is
> outside the trust boundary again.
The bit reflects how the kernel expects the device to do DMA. It does
not change when the TDISP state changes.
A device that falls to error can no longer do T=1 DMA, the device is
expected to halt that internally. It must not start doing T=0 DMA in
error either or it will corrupt random shared memory since T=0/T=1 are
different IOVA spaces on ARM and Intel.
To recover out of error the userpace would have to cycle it through
err/unlocked/locked/run and tell the kernel driver to start it up
again. During that time the device must not do any T=0 DMA because
nothing has been mapped to it in the T=0 regime.
From the driver perspecitve the device simply stops doing DMA for a
while and when it comes back in RUN it is able to do DMA again. It is
sort of like existing RAS flows where a device crashes.
Jason
next prev parent reply other threads:[~2026-09-17 13:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-10 3:32 [PATCH v1 0/8] iommu/arm-smmu-v3: Support guest-level Realm VSMMU (Part-1) Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 1/8] firmware: arm_rmm: Move RSI support out of arch/arm64 Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 2/8] firmware: arm_rmm: Add VSMMU commands and fields Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 3/8] dma-mapping: Let a device declare that it reaches private memory Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 4/8] dma-mapping: Keep DMA memory private for capable devices Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 5/8] iommu: Let a driver mark an IOMMU as confidential Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 6/8] iommu: Introduce TDISP T=0 state for confidential IOMMUs Nicolin Chen
2026-09-17 10:48 ` sonang patel
2026-09-17 13:34 ` Jason Gunthorpe [this message]
2026-09-10 3:32 ` [PATCH v1 7/8] iommu: Park TDISP T=0 devices in the blocking domain Nicolin Chen
2026-09-10 3:32 ` [PATCH v1 8/8] iommu/arm-smmu-v3: Probe a guest-level Realm VSMMU via RSI commands Nicolin Chen
2026-09-10 4:23 ` Nicolin Chen
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=20260917133458.GB3968357@nvidia.com \
--to=jgg@nvidia.com \
--cc=akpm@linux-foundation.org \
--cc=amhetre@nvidia.com \
--cc=aneesh.kumar@kernel.org \
--cc=ankita@nvidia.com \
--cc=anshuman.khandual@arm.com \
--cc=ardb@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=cfsworks@gmail.com \
--cc=chenhuacai@kernel.org \
--cc=dakr@kernel.org \
--cc=dianders@chromium.org \
--cc=driver-core@lists.linux.dev \
--cc=ekffu200098@gmail.com \
--cc=enju.kohei@fujitsu.com \
--cc=florian.fainelli@broadcom.com \
--cc=gregkh@linuxfoundation.org \
--cc=gshan@redhat.com \
--cc=iommu@lists.linux.dev \
--cc=james.morse@arm.com \
--cc=joro@8bytes.org \
--cc=kas@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=nicolinc@nvidia.com \
--cc=osandov@fb.com \
--cc=praan@google.com \
--cc=rafael@kernel.org \
--cc=robin.murphy@arm.com \
--cc=rppt@kernel.org \
--cc=ruanjinjie@huawei.com \
--cc=ryan.roberts@arm.com \
--cc=sdonthineni@nvidia.com \
--cc=skolothumtho@nvidia.com \
--cc=smostafa@google.com \
--cc=sonangp@nvidia.com \
--cc=steven.price@arm.com \
--cc=suzuki.poulose@arm.com \
--cc=tan.shaopeng@jp.fujitsu.com \
--cc=thuth@redhat.com \
--cc=tzimmermann@suse.de \
--cc=vsethi@nvidia.com \
--cc=wenst@chromium.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
all inboxes | Powered by JetHome®