linux-kernel - RE: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface

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Date: Fri, 12 Apr 2024 03:38:01 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Baolu Lu <baolu.lu@...ux.intel.com>, Jason Gunthorpe <jgg@...pe.ca>
CC: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, "Robin
 Murphy" <robin.murphy@....com>, "Zhang, Tina" <tina.zhang@...el.com>, "Liu,
 Yi L" <yi.l.liu@...el.com>, "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 01/12] iommu/vt-d: Add cache tag assignment interface

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Thursday, April 11, 2024 8:39 PM
> 
> On 2024/4/10 23:41, Jason Gunthorpe wrote:
> >> +struct cache_tag {
> >> +	struct list_head node;
> >> +	enum cache_tag_type type;
> >> +	struct intel_iommu *iommu;
> >> +	struct device *dev;
> > iommu and dev probably don't both need to be stored together. We have
> > iommu_get_iommu_dev() now.. I suppose this is probably a union of the
> > two pointers depending on tag. DEVTLB needs the dev and IOTLB needs
> > the iommu.
> 
> I forgot to reply this comment in previous reply. Sorry about it.
> 
> struct cache_tag {
>          [ ... ]
>          struct intel_iommu *iommu;
>          struct device *dev;
>          [ ... ]
> };
> 
> I treat @iommu as the queued invalidation interface. All cache
> invalidation raises to hardware through the invalidation queue.
> 
> The @dev field represents the location of the cache. For IOTLB cache, it
> resides on the IOMMU hardware. In this case, the field stores the device
> pointer to the IOMMU hardware. For DevTLB cache, it locates in the PCIe
> endpoint. Here, the field stores the device pointer to that endpoint.
> 
> A correctly set @dev pointer allows users to see more accurate trace
> message.
> 

it's not a bad to add a comment for @dev here.