linux-kernel - Re: [PATCH v2 06/19] drivers core: Add I/O ASID allocator

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Message-ID: <20190426095846.76a68f1f@jacob-builder>
Date:   Fri, 26 Apr 2019 09:58:46 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "christian.koenig@....com" <christian.koenig@....com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v2 06/19] drivers core: Add I/O ASID allocator

On Fri, 26 Apr 2019 05:21:15 -0700
Christoph Hellwig <hch@...radead.org> wrote:

> On Fri, Apr 26, 2019 at 12:47:43PM +0100, Jean-Philippe Brucker wrote:
> > >> On Tue, Apr 23, 2019 at 04:31:06PM -0700, Jacob Pan wrote:  
> > >>> The allocator doesn't really belong in drivers/iommu because
> > >>> some drivers would like to allocate PASIDs for devices that
> > >>> aren't managed by an IOMMU, using the same ID space as IOMMU.
> > >>> It doesn't really belong in drivers/pci either since platform
> > >>> device also support PASID. Add the allocator in
> > >>> drivers/base.    
> > >>
> > >> I'd still add it to drivers/iommu, just selectable separately
> > >> from the core iommu code..  
> > > Perhaps I misunderstood. If a driver wants to use IOASIDs w/o
> > > iommu subsystem even turned on, how could selecting from the core
> > > iommu code help? Could you elaborate on "selectable"?  
> > 
> > How about doing the same as CONFIG_IOMMU_IOVA? The code is in
> > drivers/iommu but can be selected by non-IOMMU_API users,
> > independently of CONFIG_IOMMU_SUPPORT. It's true that this
> > allocator will mostly be used by IOMMU drivers.  
> 
> That is exactly what I meant!

Make sense, will do that in the next round. Thanks!