linux-kernel - Re: [RESEND PATCH v6 2/3] iommu/arm: Add BBM Level 2 smmu feature

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Message-ID: <20250506141949.GA1197@willie-the-truck>
Date: Tue, 6 May 2025 15:19:49 +0100
From: Will Deacon <will@...nel.org>
To: Mikołaj Lenczewski <miko.lenczewski@....com>
Cc: ryan.roberts@....com, suzuki.poulose@....com,
	yang@...amperecomputing.com, corbet@....net,
	catalin.marinas@....com, jean-philippe@...aro.org,
	robin.murphy@....com, joro@...tes.org, akpm@...ux-foundation.org,
	paulmck@...nel.org, mark.rutland@....com, joey.gouly@....com,
	maz@...nel.org, james.morse@....com, broonie@...nel.org,
	oliver.upton@...ux.dev, baohua@...nel.org, david@...hat.com,
	ioworker0@...il.com, jgg@...pe.ca, nicolinc@...dia.com,
	mshavit@...gle.com, jsnitsel@...hat.com, smostafa@...gle.com,
	kevin.tian@...el.com, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux.dev
Subject: Re: [RESEND PATCH v6 2/3] iommu/arm: Add BBM Level 2 smmu feature

On Mon, Apr 28, 2025 at 03:35:16PM +0000, Mikołaj Lenczewski wrote:
> For supporting BBM Level 2 for userspace mappings, we want to ensure
> that the smmu also supports its own version of BBM Level 2. Luckily, the
> smmu spec (IHI 0070G 3.21.1.3) is stricter than the aarch64 spec (DDI
> 0487K.a D8.16.2), so already guarantees that no aborts are raised when
> BBM level 2 is claimed.
> 
> Add the feature and testing for it under arm_smmu_sva_supported().
> 
> Signed-off-by: Mikołaj Lenczewski <miko.lenczewski@....com>
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 3 +++
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c     | 3 +++
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h     | 4 ++++
>  3 files changed, 10 insertions(+)

This looks fine to me but please note that it doesn't apply against
mainline (v6.15-rc5).

Will