linux-kernel - Re: [PATCH v4 6/7] iommu/arm-smmu-v3: Add arm_smmu_invs based arm_smmu_domain_inv

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Message-ID: <20251108005057.GE1932966@nvidia.com>
Date: Fri, 7 Nov 2025 20:50:57 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: will@...nel.org, jean-philippe@...aro.org, robin.murphy@....com,
	joro@...tes.org, balbirs@...dia.com, miko.lenczewski@....com,
	peterz@...radead.org, kevin.tian@...el.com, praan@...gle.com,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/7] iommu/arm-smmu-v3: Add arm_smmu_invs based
 arm_smmu_domain_inv_range()

On Mon, Oct 27, 2025 at 11:54:20AM -0700, Nicolin Chen wrote:
> Each smmu_domain now has an arm_smmu_invs that specifies the invalidation
> steps to perform after any change the IOPTEs. This includes supports for
> basic ASID/VMID, the special case for nesting, and ATC invalidations.
> 
> Introduce a new arm_smmu_domain_inv helper iterating smmu_domain->invs to
> convert the invalidation array to commands. Any invalidation request with
> no size specified means an entire flush over a range based one.
> 
> Take advantage of the sorted array to compatible batch operations together
> to the same SMMU. For instance, ATC invaliations for multiple SIDs can be
> pushed as a batch.
> 
> ATC invalidations must be completed before the driver disables ATS. Or the
> device is permitted to ignore any racing invalidation that would cause an
> SMMU timeout. The sequencing is done with a rwlock where holding the write
> side of the rwlock means that there are no outstanding ATC invalidations.
> If ATS is not used the rwlock is ignored, similar to the existing code.
> 
> Co-developed-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |   9 +
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 225 ++++++++++++++++++--
>  2 files changed, 221 insertions(+), 13 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason