linux-kernel - Re: [PATCH v3 4/4] iommu/vt-d: Introduce batched cache invalidation

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Message-ID: <20240816093846.40dbd623@DESKTOP-0403QTC.>
Date: Fri, 16 Aug 2024 09:38:46 -0700
From: Jacob Pan <jacob.pan@...ux.microsoft.com>
To: Tina Zhang <tina.zhang@...el.com>
Cc: Lu Baolu <baolu.lu@...ux.intel.com>, Kevin Tian <kevin.tian@...el.com>,
 iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/4] iommu/vt-d: Introduce batched cache invalidation

On Thu, 15 Aug 2024 14:52:21 +0800
Tina Zhang <tina.zhang@...el.com> wrote:

> @@ -270,7 +343,8 @@ static void cache_tag_flush_iotlb(struct
> dmar_domain *domain, struct cache_tag * u64 type = DMA_TLB_PSI_FLUSH;
>  
>  	if (domain->use_first_level) {
> -		qi_flush_piotlb(iommu, tag->domain_id, tag->pasid,
> addr, pages, ih);
> +		qi_batch_add_piotlb(iommu, tag->domain_id,
> tag->pasid, addr,
> +				    pages, ih, domain->qi_batch);
>  		return;
>  	}
>  
> @@ -287,7 +361,8 @@ static void cache_tag_flush_iotlb(struct
> dmar_domain *domain, struct cache_tag * }
>  
>  	if (ecap_qis(iommu->ecap))
> -		qi_flush_iotlb(iommu, tag->domain_id, addr | ih,
> mask, type);
> +		qi_batch_add_iotlb(iommu, tag->domain_id, addr | ih,
> mask, type,
> +				   domain->qi_batch);
>  
If I understand this correctly, IOTLB flush maybe deferred until the
batch array is full, right? If so, is there a security gap where
callers think the mapping is gone after the call returns?