From: Jason Gunthorpe <jgg@nvidia.com>
To: Will Deacon <will@kernel.org>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
robin.murphy@arm.com, joro@8bytes.org,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, skolothumtho@nvidia.com,
praan@google.com, xueshuai@linux.alibaba.com,
smostafa@google.com
Subject: Re: [PATCH rc v5 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence
Date: Wed, 7 Jan 2026 20:36:46 -0400 [thread overview]
Message-ID: <20260108003646.GA537728@nvidia.com> (raw)
In-Reply-To: <aV7OBrH-TDiGRblt@willie-the-truck>
On Wed, Jan 07, 2026 at 09:20:06PM +0000, Will Deacon wrote:
> > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 ++
> > .../iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c | 18 ++++++++++---
> > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 27 ++++++++++++++-----
> > 3 files changed, 37 insertions(+), 10 deletions(-)
>
> Hmm. So this appears to ignore the safe bits entirely, whereas the
> rationale for the change is that going from {MEV,EATS} disabled to
> enabled is safe (which I agree with).
The argument was it doesn't matter for either direction be it disabled
to enabled or vice versa, see my reply to Mustfa in the v4 posting:
https://lore.kernel.org/all/20251218180129.GA254720@nvidia.com/
> So what prevents an erroneous hitless STE update when going from
> {MEV,EATS} enabled to disabled after this change?
Nothing, it isn't erroneous.
Jason
next prev parent reply other threads:[~2026-01-08 0:37 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-18 21:41 [PATCH rc v5 0/4] iommu/arm-smmu-v3: Fix hitless STE update in nesting cases Nicolin Chen
2025-12-18 21:41 ` [PATCH rc v5 1/4] iommu/arm-smmu-v3: Add update_safe bits to fix STE update sequence Nicolin Chen
2026-01-02 18:26 ` Mostafa Saleh
2026-01-07 21:20 ` Will Deacon
2026-01-08 0:36 ` Jason Gunthorpe [this message]
2026-01-12 15:53 ` Will Deacon
2026-01-12 16:10 ` Jason Gunthorpe
2026-01-12 18:58 ` Nicolin Chen
2026-01-13 15:05 ` Will Deacon
2026-01-13 16:12 ` Jason Gunthorpe
2026-01-13 20:29 ` Nicolin Chen
2026-01-13 20:51 ` Jason Gunthorpe
2026-01-15 13:11 ` Jason Gunthorpe
2026-01-15 16:25 ` Nicolin Chen
2026-01-15 16:29 ` Jason Gunthorpe
2026-01-15 16:34 ` Nicolin Chen
2026-01-15 17:39 ` Will Deacon
2025-12-18 21:41 ` [PATCH rc v5 2/4] iommu/arm-smmu-v3: Mark STE MEV safe when computing the " Nicolin Chen
2026-01-02 18:27 ` Mostafa Saleh
2025-12-18 21:41 ` [PATCH rc v5 3/4] iommu/arm-smmu-v3: Mark STE EATS " Nicolin Chen
2025-12-18 21:41 ` [PATCH rc v5 4/4] iommu/arm-smmu-v3-test: Add nested s1bypass/s1dssbypass coverage Nicolin Chen
2026-01-02 18:27 ` Mostafa Saleh
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