linux-kernel - Re: [PATCH RFCv2 06/13] iommufd: Make attach

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Message-ID: <Z4wP8ad/4Q5wMryd@nvidia.com>
Date: Sat, 18 Jan 2025 12:32:49 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Yi Liu <yi.l.liu@...el.com>, <jgg@...dia.com>
CC: <will@...nel.org>, <robin.murphy@....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>,
	<eric.auger@...hat.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 06/13] iommufd: Make attach_handle generic

On Sat, Jan 18, 2025 at 04:23:22PM +0800, Yi Liu wrote:
> On 2025/1/11 11:32, Nicolin Chen wrote:
> > "attach_handle" was added exclusively for the iommufd_fault_iopf_handler()
> > used by IOPF/PRI use cases, along with the "fault_data". Now, the iommufd
> > version of sw_msi function will resue the attach_handle and fault_data for
> > a non-fault case.
> > 
> > Move the attach_handle part out of the fault.c file to make it generic for
> > all cases. Simplify the remaining fault specific routine to attach/detach.
> 
> I guess you can send it separately since both of our series need it. :)

Jason, would you like to take this patch separately? I can send
it prior to two big series for a quick review after rc1. It'll
likely impact the vEVENTQ series too.

> > +static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
> > +				      struct iommufd_device *idev)
> > +{
> > +	struct iommufd_attach_handle *handle;
> > +	int rc;
> > +
> > +	if (hwpt->fault) {
> > +		rc = iommufd_fault_domain_attach_dev(hwpt, idev, true);
> > +		if (rc)
> > +			return rc;
> > +	}
> > +
> > +	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> > +	if (!handle) {
> > +		rc = -ENOMEM;
> > +		goto out_fault_detach;
> > +	}
> > +
> > +	handle->idev = idev;
> > +	rc = iommu_attach_group_handle(hwpt->domain, idev->igroup->group,
> > +				       &handle->handle);
> > +	if (rc)
> > +		goto out_free_handle;
> > +
> > +	return 0;
> > +
> > +out_free_handle:
> > +	kfree(handle);
> > +	handle = NULL;
> > +out_fault_detach:
> > +	if (hwpt->fault)
> > +		iommufd_fault_domain_detach_dev(hwpt, idev, handle, true);
> > +	return rc;
> > +}

Here the revert path passes in a handle=NULL..

> >   void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable *hwpt,
> > -				     struct iommufd_device *idev)
> > +				     struct iommufd_device *idev,
> > +				     struct iommufd_attach_handle *handle,
> > +				     bool disable_iopf)
> >   {
> > +	if (handle)
> > +		iommufd_auto_response_faults(hwpt, handle);
> 
> no need to check handle. After this patch, both the non-fault and the fault
> path will allocate handle. It cannot be used to isolate fault and non-fault
> path. Also, the callers of iommufd_fault_domain_detach_dev() will check
> hwpt->fault before calling it. So just call iommufd_auto_response_faults().

..so we still need this !NULL validation? :-/

Thanks
Nicolin