From: Will Deacon <will@kernel.org>
To: Nicolin Chen <nicolinc@nvidia.com>
Cc: catalin.marinas@arm.com, kernel-team@android.com,
"Will Deacon" <will@kernel.org>, "Joerg Roedel" <joro@8bytes.org>,
"Jean-Philippe Brucker" <jpb@kernel.org>,
"Robin Murphy" <robin.murphy@arm.com>,
"Pranjal Shrivastava" <praan@google.com>,
"Mikołaj Lenczewski" <miko.lenczewski@arm.com>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, "Jason Gunthorpe" <jgg@ziepe.ca>
Subject: Re: [PATCH] iommu/arm-smmu-v3-sva: Enable Hardware Access and Hardware Dirty bits
Date: Tue, 19 May 2026 16:23:07 +0100 [thread overview]
Message-ID: <177919969031.1013920.6454574496615860619.b4-ty@kernel.org> (raw)
In-Reply-To: <20260503135413.1108138-1-nicolinc@nvidia.com>
On Sun, 03 May 2026 06:54:12 -0700, Nicolin Chen wrote:
> HTTU is introduced by utilizing the Dirty Bit Modifier (DBM) in the PTE.
> When kernel maps a clean but writable page, it will set PTE_READONLY and
> PTE_DBM (aka PTE_WRITE) at the same time. When a write occurs, an HTTU-
> capable MMU will automatically clear the PTE_RDONLY bit without software
> intervention.
>
> On the other hand, SMMU has the same HTTU feature, yet it is not enabled
> in the SVA CD. As a result, SMMU will not clear the PTE_RDONLY bit while
> sharing the CPU page table, resulting in unnecessary stalls.
>
> [...]
Applied to iommu (arm/smmu/updates), thanks!
[1/1] iommu/arm-smmu-v3-sva: Enable Hardware Access and Hardware Dirty bits
https://git.kernel.org/iommu/c/74fa4c177ad0
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
prev parent reply other threads:[~2026-05-19 15:25 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-03 13:54 [PATCH] iommu/arm-smmu-v3-sva: Enable Hardware Access and Hardware Dirty bits Nicolin Chen
2026-05-07 22:30 ` Pranjal Shrivastava
2026-05-08 12:35 ` Jason Gunthorpe
2026-05-08 13:12 ` Pranjal Shrivastava
2026-05-08 13:27 ` Jason Gunthorpe
2026-05-08 13:31 ` Robin Murphy
2026-05-08 13:57 ` Pranjal Shrivastava
2026-05-08 14:24 ` Robin Murphy
2026-05-09 7:56 ` Nicolin Chen
2026-05-11 13:22 ` Pranjal Shrivastava
2026-05-13 11:42 ` Will Deacon
2026-05-13 14:27 ` Pranjal Shrivastava
2026-05-13 14:32 ` Jason Gunthorpe
2026-05-13 17:38 ` Pranjal Shrivastava
2026-05-11 13:21 ` Pranjal Shrivastava
2026-05-19 15:23 ` Will Deacon [this message]
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