linux-kernel - Re: [PATCH v2 12/12] iommu/vt-d: Retire struct intel

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Date: Wed, 10 Apr 2024 12:49:51 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Kevin Tian <kevin.tian@...el.com>,
	Tina Zhang <tina.zhang@...el.com>, Yi Liu <yi.l.liu@...el.com>,
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/12] iommu/vt-d: Retire struct intel_svm

On Wed, Apr 10, 2024 at 10:08:44AM +0800, Lu Baolu wrote:
> The struct intel_svm was used for keeping attached devices info for sva
> domain. Since sva domain is a kind of iommu_domain, the struct
> dmar_domain should centralize all info of a sva domain, including the
> info of attached devices. Therefore, retire struct intel_svm to clean up
> the code.
> 
> Besides, allocate sva domain in domain_alloc_sva() callback which allows
> the memory management notifier lifetime to follow the lifetime of the
> iommu_domain.
> 
> Co-developed-by: Tina Zhang <tina.zhang@...el.com>
> Signed-off-by: Tina Zhang <tina.zhang@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel/iommu.h | 26 ++++------
>  drivers/iommu/intel/iommu.c |  9 +---
>  drivers/iommu/intel/svm.c   | 94 +++++++++----------------------------
>  3 files changed, 32 insertions(+), 97 deletions(-)

Happy to see the pasid xarray in the driver go away.

> @@ -4388,14 +4386,8 @@ static void intel_iommu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
>  	WARN_ON_ONCE(!dev_pasid);
>  	spin_unlock_irqrestore(&dmar_domain->lock, flags);
>  
> -	/*
> -	 * The SVA implementation needs to handle its own stuffs like the mm
> -	 * notification. Before consolidating that code into iommu core, let
> -	 * the intel sva code handle it.
> -	 */
>  	if (domain->type == IOMMU_DOMAIN_SVA) {
>  		cache_tag_unassign_domain(dmar_domain, FLPT_DEFAULT_DID, dev, pasid);
> -		intel_svm_remove_dev_pasid(domain);
>  	} else {
>  		did = domain_id_iommu(dmar_domain, iommu);
>  		cache_tag_unassign_domain(dmar_domain, did, dev, pasid);

It seems very strange that SVA has a different DID scheme, why is
this? PASID and SVA should not be different at this layer.

> @@ -663,7 +596,12 @@ void intel_svm_page_response(struct device *dev, struct iopf_fault *evt,
>  
>  static void intel_svm_domain_free(struct iommu_domain *domain)
>  {
> -	kfree(to_dmar_domain(domain));
> +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> +
> +	if (dmar_domain->notifier.ops)
> +		mmu_notifier_unregister(&dmar_domain->notifier, domain->mm);

This should really use mmu_notifier_put() and a delayed kfree, see my
part 2 ARM series for how that should look.

Otherwise I think it looks fine

Jason