linux-kernel - Re: [PATCH v3 5/8] iommufd: Associate fault object with iommufd_hw

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Date: Fri, 8 Mar 2024 13:19:44 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Baolu Lu <baolu.lu@...ux.intel.com>
Cc: Zhangfei Gao <zhangfei.gao@...aro.org>,
	Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Nicolin Chen <nicolinc@...dia.com>, Yi Liu <yi.l.liu@...el.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Joel Granados <j.granados@...sung.com>, iommu@...ts.linux.dev,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/8] iommufd: Associate fault object with
 iommufd_hw_pgtable

On Thu, Mar 07, 2024 at 09:54:53AM +0800, Baolu Lu wrote:
> On 2024/3/7 0:01, Jason Gunthorpe wrote:
> > On Wed, Mar 06, 2024 at 11:15:50PM +0800, Zhangfei Gao wrote:
> > > Double checked, this does not send flags, 0 is OK,
> > > Only domain_alloc_user in iommufd_hwpt_paging_alloc requires flags.
> > > 
> > > In my debug, I need this patch, otherwise NULL pointer errors happen
> > > since SVA is not set.
> > This is some driver bug, we need to get rid of these
> > iommu_dev_enable_feature() requirements.
> 
> Yes. Especially iopf should be independent of SVA.
> 
> The problem in the arm smmu v3 driver is that enabling iopf is actually
> done in the enabling SVA path, while the enabling iopf path does nothing
> except for some checks. It doesn't matter if iopf is tied with SVA, but
> when it comes to delivering iopf to user space, we need to decouple it.

Yes. Each driver is going to need to get a to a NOP for the feature
things then we can remove them.

I did half the ARM driver in my part 2, the iopf bit still needs
doing there.

Jason