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

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Date: Thu, 7 Mar 2024 09:54:53 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Jason Gunthorpe <jgg@...pe.ca>, Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: baolu.lu@...ux.intel.com, 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 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.

Best regards,
baolu