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Date:   Fri, 20 Sep 2019 18:33:27 +0200
From:   Jean-Philippe Brucker <jean-philippe@linaro.org>
To:     Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc:     iommu@lists.linux-foundation.org,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Jonathan Cameron <jic23@kernel.org>
Subject: Re: [PATCH 2/4] iommu: Add I/O ASID allocator
Message-ID: <20190920163327.GB1533866@lophozonia>
References: <1568849194-47874-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1568849194-47874-3-git-send-email-jacob.jun.pan@linux.intel.com>
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On Wed, Sep 18, 2019 at 04:26:32PM -0700, Jacob Pan wrote:
> From: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> 
> Some devices might support multiple DMA address spaces, in particular
> those that have the PCI PASID feature. PASID (Process Address Space ID)
> allows to share process address spaces with devices (SVA), partition a
> device into VM-assignable entities (VFIO mdev) or simply provide
> multiple DMA address space to kernel drivers. Add a global PASID
> allocator usable by different drivers at the same time. Name it I/O ASID
> to avoid confusion with ASIDs allocated by arch code, which are usually
> a separate ID space.
> 
> The IOASID space is global. Each device can have its own PASID space,
> but by convention the IOMMU ended up having a global PASID space, so
> that with SVA, each mm_struct is associated to a single PASID.
> 
> The allocator is primarily used by IOMMU subsystem but in rare occasions
> drivers would like to allocate PASIDs for devices that aren't managed by
> an IOMMU, using the same ID space as IOMMU.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>

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