linux-kernel - Re: [PATCH v2 17/19] iommu/arm-smmu-v3: Add arm_smmu_viommu_cache

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Message-ID: <20240905162039.GT1358970@nvidia.com>
Date: Thu, 5 Sep 2024 13:20:39 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com, shuah@...nel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com
Subject: Re: [PATCH v2 17/19] iommu/arm-smmu-v3: Add
 arm_smmu_viommu_cache_invalidate

On Tue, Aug 27, 2024 at 09:59:54AM -0700, Nicolin Chen wrote:

> +static int arm_smmu_viommu_cache_invalidate(struct iommufd_viommu *viommu,
> +					    struct iommu_user_data_array *array)
> +{
> +	struct iommu_domain *domain = iommufd_viommu_to_parent_domain(viommu);
> +
> +	return __arm_smmu_cache_invalidate_user(
> +			to_smmu_domain(domain), viommu, array);

I'd like to have the viommu struct directly hold the VMID. The nested
parent should be sharable between multiple viommus, it doesn't make
any sense that it would hold the vmid.

This is struggling because it is trying too hard to not have the
driver allocate the viommu, and I think we should just go ahead and do
that. Store the vmid, today copied from the nesting parent in the vmid
private struct. No need for iommufd_viommu_to_parent_domain(), just
rework the APIs to pass the vmid down not a domain.

Jason