linux-kernel - Re: [PATCH v1 07/10] iommu/vt-d: Use an xarray for global device_domain

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Date:   Mon, 7 Feb 2022 08:14:20 +0100
From:   Christoph Hellwig <hch@....de>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Liu Yi L <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@....de>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 07/10] iommu/vt-d: Use an xarray for global
 device_domain_info

> + #define DEVI_IDX(seg, bus, devfn) ((((u16)(seg)) << 16) | PCI_DEVID(bus, devfn))

Please turn this into an real function.
>  /*
> - * Iterate over elements in device_domain_list and call the specified
> + * Iterate over elements in device_domain_array and call the specified
>   * callback @fn against each element.
>   */
>  int for_each_device_domain(int (*fn)(struct device_domain_info *info,
>  				     void *data), void *data)
>  {
>  	struct device_domain_info *info;
> +	unsigned long index;
> +	int ret = 0;
>  
> +	rcu_read_lock();
> +	xa_for_each(&device_domain_array, index, info) {
>  		ret = fn(info, data);
> +		if (ret)
> +			break;
>  	}
> +	rcu_read_unlock();

Can't we just open code this in the caller now?

>  const struct iommu_ops intel_iommu_ops;
> @@ -900,7 +898,8 @@ static void pgtable_walk(struct intel_iommu *iommu, unsigned long pfn, u8 bus, u
>  	struct dmar_domain *domain;
>  	int offset, level;
>  
> -	info = dmar_search_domain_by_dev_info(iommu->segment, bus, devfn);
> +	info = xa_load(&device_domain_array,
> +		       DEVI_IDX(iommu->segment, bus, devfn));
>  	if (!info || !info->domain) {
>  		pr_info("device [%02x:%02x.%d] not probed\n",
>  			bus, PCI_SLOT(devfn), PCI_FUNC(devfn));

Is there any refcounting or other life time protection for the info
structures?