linux-kernel - Re: [PATCH v1 11/14] iommu/arm-smmu-v3: Add arm_smmu_domain_alloc

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Message-ID: <ZB3lJYGjkI2Qr4X7@Asurada-Nvidia>
Date:   Fri, 24 Mar 2023 11:00:05 -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 11/14] iommu/arm-smmu-v3: Add
 arm_smmu_domain_alloc_user

On Fri, Mar 24, 2023 at 02:50:42PM -0300, Jason Gunthorpe wrote:
> On Fri, Mar 24, 2023 at 10:40:46AM -0700, Nicolin Chen wrote:
> > Hi Eirc,
> > 
> > Thanks for the review.
> > 
> > On Fri, Mar 24, 2023 at 04:28:26PM +0100, Eric Auger wrote:
> > 
> > > > +static struct iommu_domain *
> > > > +__arm_smmu_domain_alloc(unsigned type,
> > > > +                     struct arm_smmu_domain *s2,
> > > > +                     struct arm_smmu_master *master,
> > > > +                     const struct iommu_hwpt_arm_smmuv3 *user_cfg)
> > > > +{
> > > > +     struct arm_smmu_domain *smmu_domain;
> > > > +     struct iommu_domain *domain;
> > > > +     int ret = 0;
> > > > +
> > > > +     if (type == IOMMU_DOMAIN_SVA)
> > > > +             return arm_smmu_sva_domain_alloc();
> > > > +
> > > > +     if (type != IOMMU_DOMAIN_UNMANAGED &&
> > > > +         type != IOMMU_DOMAIN_DMA &&
> > > > +         type != IOMMU_DOMAIN_DMA_FQ &&
> > > > +         type != IOMMU_DOMAIN_IDENTITY)
> > > > +             return NULL;
> > > > +
> > > > +     /*
> > > > +      * Allocate the domain and initialise some of its data structures.
> > > > +      * We can't really finalise the domain unless a master is given.
> > > > +      */
> > > > +     smmu_domain = kzalloc(sizeof(*smmu_domain), GFP_KERNEL);
> > > > +     if (!smmu_domain)
> > > > +             return NULL;
> > > > +     domain = &smmu_domain->domain;
> > > > +
> > > > +     domain->type = type;
> > > > +     domain->ops = arm_smmu_ops.default_domain_ops;
> > > Compared to the original code, that's something new. Please can you
> > > explain why this is added in this patch?
> > 
> > Yea, I probably should have mentioned in the commit message that
> > this function via ops->domain_alloc_user() is called by IOMMUFD
> > directly without a wrapper, v.s. the other callers all go with
> > the __iommu_domain_alloc() helper in the iommu core where an ops
> > pointer gets setup.
> > 
> > So, this is something new, in order to work with IOMMUFD.
> 
> But using default_domain_ops is not great, the ops should be set based
> on the domain type being created and the various different flavours
> should have their own types and ops.
> 
> So name the existing ops something logical like 'unmanaged_domain_ops'
> and move it out of the inline initializer.
> 
> Make another ops for identity like shown here to get the ball rolling:
> 
>  https://lore.kernel.org/r/20230324111127.221640-1-steven.price@arm.com
> 
> There is a whole bunch of tidying here to make things follow the op
> per type design.

Thanks for the suggestion. Will add a patch doing that in v2.

Nicolin