linux-kernel - Re: [PATCH v4 3/4] iommu/ioasid: Add custom allocators

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Message-ID: <20191004171835.GB1180125@lophozonia>
Date:   Fri, 4 Oct 2019 19:18:35 +0200
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        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>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>
Subject: Re: [PATCH v4 3/4] iommu/ioasid: Add custom allocators

On Wed, Oct 02, 2019 at 12:42:42PM -0700, Jacob Pan wrote:
> IOASID allocation may rely on platform specific methods. One use case is
> that when running in the guest, in order to obtain system wide global
> IOASIDs, emulated allocation interface is needed to communicate with the
> host. Here we call these platform specific allocators custom allocators.
> 
> Custom IOASID allocators can be registered at runtime and take precedence
> over the default XArray allocator. They have these attributes:
> 
> - provides platform specific alloc()/free() functions with private data.
> - allocation results lookup are not provided by the allocator, lookup
>   request must be done by the IOASID framework by its own XArray.
> - allocators can be unregistered at runtime, either fallback to the next
>   custom allocator or to the default allocator.
> - custom allocators can share the same set of alloc()/free() helpers, in
>   this case they also share the same IOASID space, thus the same XArray.
> - switching between allocators requires all outstanding IOASIDs to be
>   freed unless the two allocators share the same alloc()/free() helpers.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Link: https://lkml.org/lkml/2019/4/26/462

Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>