linux-kernel - Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN

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Message-ID: <ZB3kD//ugNBy4En7@Asurada-Nvidia>
Date:   Fri, 24 Mar 2023 10:55:27 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     Eric Auger <eric.auger@...hat.com>, <robin.murphy@....com>,
        <will@...nel.org>, <kevin.tian@...el.com>,
        <baolu.lu@...ux.intel.com>, <joro@...tes.org>,
        <shameerali.kolothum.thodi@...wei.com>, <jean-philippe@...aro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED
 type of allocations

On Fri, Mar 24, 2023 at 02:51:45PM -0300, Jason Gunthorpe wrote:
> On Fri, Mar 24, 2023 at 10:50:34AM -0700, Nicolin Chen wrote:
> > On Fri, Mar 24, 2023 at 04:44:58PM +0100, Eric Auger wrote:
> > > > @@ -2923,8 +2949,16 @@ arm_smmu_domain_alloc_user(struct device *dev, struct iommu_domain *parent,
> > > >       const struct iommu_hwpt_arm_smmuv3 *user_cfg = user_data;
> > > >       struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> > > >       unsigned type = IOMMU_DOMAIN_UNMANAGED;
> > > > +     struct arm_smmu_domain *s2 = NULL;
> > > > +
> > > > +     if (parent) {
> > > > +             if (parent->ops != arm_smmu_ops.default_domain_ops)
> > > > +                     return NULL;
> > > > +             type = IOMMU_DOMAIN_NESTED;
> > > > +             s2 = to_smmu_domain(parent);
> > > > +     }
> > > Please can you explain the (use) case where !parent. This creates an
> > > unmanaged S1?
> > 
> > It creates an unmanaged type of a domain. The decision to mark
> > it as an unmanaged S1 or an unmanaged S2 domain, is done in the
> > finalise() function that it checks the S2 flag and set a stage
> > accordingly.
> 
> This also needs to be fixed up, the alloc_user should not return
> incompletely initialized domains.

The finalise() is called at the end of __arm_smmu_domain_alloc()
so alloc_user passing a dev pointer completes the initialization
actually.

Thanks
Nicolin