linux-kernel - Re: [PATCH v2 04/10] iommu/arm-smmu-v3: Allocate IOTLB cache tag if no id to reuse

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20260127162908.GL1134360@nvidia.com>
Date: Tue, 27 Jan 2026 12:29:08 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: will@...nel.org, robin.murphy@....com, joro@...tes.org, jpb@...nel.org,
	praan@...gle.com, miko.lenczewski@....com,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v2 04/10] iommu/arm-smmu-v3: Allocate IOTLB cache tag if
 no id to reuse

On Mon, Jan 26, 2026 at 02:23:36PM -0800, Nicolin Chen wrote:
> On Mon, Jan 26, 2026 at 05:06:40PM -0400, Jason Gunthorpe wrote:
> > On Wed, Jan 21, 2026 at 05:24:22PM -0800, Nicolin Chen wrote:
> > > @@ -3220,6 +3241,9 @@ arm_smmu_master_build_inv(struct arm_smmu_master *master,
> > >  		break;
> > >  	}
> > >  
> > > +	/* Set a default users counter */
> > > +	refcount_set(&cur->users, 1);
> > 
> > I think abusing users here is a little too hard to read..
> > 
> > Can we just keep track in the state somehow with a flag?
> >
> > Or maybe union in a "bool needs_free" that is for the on-stack version
> > of this structure?
> 
> This doesn't only apply to the case when a tag is newly allocated
> during the attach, but it can be used when an old tag has users=0
> during a detach, right?

Oh, IDK, I didn't look so closely..

I though this was just about cleaning up the tag during attach, the
detach flow worked differently and did use users = 0?

Jason