linux-kernel - Re: [PATCH RFCv2 05/13] iommu: Turn fault

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Message-ID: <Z6EBdDbMZqh+9NOL@Asurada-Nvidia>
Date: Mon, 3 Feb 2025 09:48:36 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Eric Auger <eric.auger@...hat.com>
CC: <will@...nel.org>, <robin.murphy@....com>, <jgg@...dia.com>,
	<kevin.tian@...el.com>, <tglx@...utronix.de>, <maz@...nel.org>,
	<alex.williamson@...hat.com>, <joro@...tes.org>, <shuah@...nel.org>,
	<reinette.chatre@...el.com>, <yebin10@...wei.com>, <apatel@...tanamicro.com>,
	<shivamurthy.shastri@...utronix.de>, <bhelgaas@...gle.com>,
	<anna-maria@...utronix.de>, <yury.norov@...il.com>, <nipun.gupta@....com>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <kvm@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>, <patches@...ts.linux.dev>,
	<jean-philippe@...aro.org>, <mdf@...nel.org>, <mshavit@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>, <smostafa@...gle.com>,
	<ddutile@...hat.com>
Subject: Re: [PATCH RFCv2 05/13] iommu: Turn fault_data to iommufd private
 pointer

Hi Eric,

On Wed, Jan 29, 2025 at 01:40:54PM +0100, Eric Auger wrote:
> On 1/11/25 4:32 AM, Nicolin Chen wrote:
> > A "fault_data" was added exclusively for the iommufd_fault_iopf_handler()
> > used by IOPF/PRI use cases, along with the attach_handle. Now, the iommufd
> > version of sw_msi function will resue the attach_handle and fault_data for
> reuse

Ack.

> > diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
> > index ce03c3804651..f7c0d7b214b6 100644
> > --- a/drivers/iommu/iommufd/hw_pagetable.c
> > +++ b/drivers/iommu/iommufd/hw_pagetable.c
> > @@ -402,10 +402,10 @@ int iommufd_hwpt_alloc(struct iommufd_ucmd *ucmd)
> >  		}
> >  		hwpt->fault = fault;
> >  		hwpt->domain->iopf_handler = iommufd_fault_iopf_handler;
> > -		hwpt->domain->fault_data = hwpt;
> >  		refcount_inc(&fault->obj.users);
> >  		iommufd_put_object(ucmd->ictx, &fault->obj);
> >  	}
> > +	hwpt->domain->iommufd_hwpt = hwpt;

> don't we want to reset this somewhere on release path?

We do iommu_domain_free() entirely on HWPT's release path.

This basically sets the domain's "owner data" as Jason remarked:
https://lore.kernel.org/linux-iommu/20250113164037.GO5556@nvidia.com/

Thanks
Nicolin