linux-kernel - RE: [PATCH 9/9] iommu: Use fault cookie to store iopf

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Date:   Tue, 11 Jul 2023 06:26:43 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Will Deacon" <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 9/9] iommu: Use fault cookie to store iopf_param

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Tuesday, July 11, 2023 9:07 AM
> 
> Remove the static iopf_param pointer from struct iommu_fault_param to
> save memory.

why is there memory saving? you replace a single pointer with a xarray now...

> @@ -303,16 +303,27 @@ int iopf_queue_add_device(struct iopf_queue
> *queue, struct device *dev)
> 
>  	mutex_lock(&queue->lock);
>  	mutex_lock(&param->lock);
> -	if (!param->iopf_param) {
> -		list_add(&iopf_param->queue_list, &queue->devices);
> -		param->iopf_param = iopf_param;
> -		ret = 0;
> +	curr = iommu_set_device_fault_cookie(dev, 0, iopf_param);
> +	if (IS_ERR(curr)) {
> +		ret = PTR_ERR(curr);
> +		goto err_free;
>  	}

So although the new xarray is called a per-pasid storage, here only
slot#0 is used for sva which includes a list containing partial req's
for many pasid's. It doesn't sound clean...