linux-kernel - Re: [PATCH v5 06/13] iommufd: Allow pt_id to carry viommu_id for IOMMU_HWPT

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Message-ID: <20241028130309.GP6956@nvidia.com>
Date: Mon, 28 Oct 2024 10:03:09 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: Nicolin Chen <nicolinc@...dia.com>, kevin.tian@...el.com,
	will@...nel.org, joro@...tes.org, suravee.suthikulpanit@....com,
	robin.murphy@....com, dwmw2@...radead.org, baolu.lu@...ux.intel.com,
	shuah@...nel.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com, aik@....com, patches@...ts.linux.dev
Subject: Re: [PATCH v5 06/13] iommufd: Allow pt_id to carry viommu_id for
 IOMMU_HWPT_ALLOC

On Mon, Oct 28, 2024 at 11:24:10AM +0800, Zhangfei Gao wrote:

> > +/**
> > + * iommufd_viommu_alloc_hwpt_nested() - Get a hwpt_nested for a vIOMMU
> > + * @viommu: vIOMMU ojbect to associate the hwpt_nested/domain with
> > + * @user_data: user_data pointer. Must be valid
> > + *
> > + * Allocate a new IOMMU_DOMAIN_NESTED for a vIOMMU and return it as a NESTED
> > + * hw_pagetable.
> > + */
> > +static struct iommufd_hwpt_nested *
> > +iommufd_viommu_alloc_hwpt_nested(struct iommufd_viommu *viommu, u32 flags,
> > +                                const struct iommu_user_data *user_data)
> > +{
> > +       struct iommufd_hwpt_nested *hwpt_nested;
> > +       struct iommufd_hw_pagetable *hwpt;
> > +       int rc;
> > +
> > +       if (flags)
> > +               return ERR_PTR(-EOPNOTSUPP);
> 
> This check should be removed.
> 
> When a user page fault is required, IOMMU_HWPT_FAULT_ID_VALID is set.
> if (cmd->flags & IOMMU_HWPT_FAULT_ID_VALID) {

It can't just be removed..

I suspect that IOMMU_HWPT_FAULT_ID_VALID should not be set on the
nested domain but on the parent?

Jason