linux-kernel - Re: [PATCH 06/10] iommu/ioasid: Convert to set aware allocations

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Message-ID: <20200401135525.GG882512@myrica>
Date:   Wed, 1 Apr 2020 15:55:25 +0200
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>
Subject: Re: [PATCH 06/10] iommu/ioasid: Convert to set aware allocations

On Wed, Mar 25, 2020 at 10:55:27AM -0700, Jacob Pan wrote:
> The current ioasid_alloc function takes a token/ioasid_set then record it
> on the IOASID being allocated. There is no alloc/free on the ioasid_set.
> 
> With the IOASID set APIs, callers must allocate an ioasid_set before
> allocate IOASIDs within the set. Quota and other ioasid_set level
> activities can then be enforced.
> 
> This patch converts existing API to the new ioasid_set model.
> 
> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>

[...]

> @@ -379,6 +391,9 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
>  	}
>  	data->id = id;
>  
> +	/* Store IOASID in the per set data */
> +	xa_store(&sdata->xa, id, data, GFP_KERNEL);

I couldn't figure out why you're maintaining an additional xarray for each
set. We're already storing that data in active_allocator->xa, why the
duplication?  If it's for the gPASID -> hPASID translation mentioned by
the cover letter, maybe you could add this xa when introducing that
change?

Thanks,
Jean