linux-kernel - Re: [PATCH v4 7/7] iommufd/selftest: Add coverage for vdevice tombstone

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Message-ID: <aG+G76s3gw5/U8iw@yilunxu-OptiPlex-7050>
Date: Thu, 10 Jul 2025 17:25:03 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
Cc: "jgg@...dia.com" <jgg@...dia.com>, "jgg@...pe.ca" <jgg@...pe.ca>,
	"will@...nel.org" <will@...nel.org>,
	"aneesh.kumar@...nel.org" <aneesh.kumar@...nel.org>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"joro@...tes.org" <joro@...tes.org>,
	"robin.murphy@....com" <robin.murphy@....com>,
	"shuah@...nel.org" <shuah@...nel.org>,
	"nicolinc@...dia.com" <nicolinc@...dia.com>,
	"aik@....com" <aik@....com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
	"Xu, Yilun" <yilun.xu@...el.com>
Subject: Re: [PATCH v4 7/7] iommufd/selftest: Add coverage for vdevice
 tombstone

On Thu, Jul 10, 2025 at 08:10:34AM +0000, Tian, Kevin wrote:
> > From: Xu Yilun <yilun.xu@...ux.intel.com>
> > Sent: Wednesday, July 9, 2025 12:03 PM
> > 
> > This tests the flow to tombstone vdevice when idevice is to be unbound
> > before vdevice destruction. The expected result is:
> > 
> >  - idevice unbinding tombstones vdevice ID, the ID can't be repurposed
> >    anymore.
> >  - Even ioctl(IOMMU_DESTROY) can't free the tombstoned ID.
> >  - iommufd_fops_release() can still free everything.
> 
> but the test only checks 2) instead of all?

It tests 2) & 3), 3) will be executed on FIXTURE_TEARDOWN(iommufd_viommu)

For 1) "the ID can't be repurposed anymore", I don't have a good idea how to
verify it. Allocate 2^32 objects and verify no tombstoned ID is
reused? That's too crazy...   Maybe just mark it untested in the commit
message?

Thanks,
Yilun