linux-kernel - Re: [PATCH 2/2] iommu/ioasid: Remove custom IOASID allocator

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Date:   Mon, 13 Feb 2023 12:24:15 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Robin Murphy <robin.murphy@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>
Subject: Re: [PATCH 2/2] iommu/ioasid: Remove custom IOASID allocator

On Mon, Feb 13, 2023 at 04:20:29PM +0000, Jean-Philippe Brucker wrote:
> On Fri, Feb 10, 2023 at 03:02:06PM -0800, Jacob Pan wrote:
> > Custom allocator feature was introduced to support VT-d's virtual
> > command, an enlightened interface designed for VMs to allocate PASIDs
> > from the host.
> > 
> > As we remove/withdraw the VT-d virtual command feature, the sole user
> > of custom allocator, we can safely remove the custom allocator as well.
> > Effectively, this will return IOASID core to the original simple global
> > namespace allocator.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> 
> You can also drop the spinlock.h include. With that:
> 
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
> 
> On a related note, it looks like 100b8a14a370 ("iommu/vt-d: Add pasid
> private data helpers") removed the last user of ioasid_set_data(). I guess
> that could be dropped too, unless you plan to still use it?
> 
> We could also merge ioasid.c into iommu-sva.c at this point, since I
> haven't seen any interest for having multiple IOASID sets on Arm, but I'm
> not sure what the current plan is for vSVA on x86.

Once the customer allocator is removed this is bascially a thin
wrapper around xarray

So anything that needs multiple pasid spaces should just create it on
its own directly with xarray

This is bascially a shared xarray for a global pasid space.

Jason