linux-kernel - Re: [PATCH v3 3/5] iommu: Add iommu_get_domain_for_dev

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 for Android: free password hash cracker in your pocket

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

Message-ID: <aKcwMtPJuFfVA8TF@Asurada-Nvidia>
Date: Thu, 21 Aug 2025 07:41:54 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
CC: "robin.murphy@....com" <robin.murphy@....com>, "joro@...tes.org"
	<joro@...tes.org>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"jgg@...dia.com" <jgg@...dia.com>, "will@...nel.org" <will@...nel.org>,
	"robin.clark@....qualcomm.com" <robin.clark@....qualcomm.com>,
	"yong.wu@...iatek.com" <yong.wu@...iatek.com>, "matthias.bgg@...il.com"
	<matthias.bgg@...il.com>, "angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>, "thierry.reding@...il.com"
	<thierry.reding@...il.com>, "vdumpa@...dia.com" <vdumpa@...dia.com>,
	"jonathanh@...dia.com" <jonathanh@...dia.com>, "rafael@...nel.org"
	<rafael@...nel.org>, "lenb@...nel.org" <lenb@...nel.org>, "Liu, Yi L"
	<yi.l.liu@...el.com>, "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "iommu@...ts.linux.dev"
	<iommu@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-arm-msm@...r.kernel.org"
	<linux-arm-msm@...r.kernel.org>, "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>, "linux-tegra@...r.kernel.org"
	<linux-tegra@...r.kernel.org>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>, "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>, "patches@...ts.linux.dev"
	<patches@...ts.linux.dev>, "Jaroszynski, Piotr" <pjaroszynski@...dia.com>,
	"Sethi, Vikram" <vsethi@...dia.com>, "helgaas@...nel.org"
	<helgaas@...nel.org>, "etzhao1900@...il.com" <etzhao1900@...il.com>
Subject: Re: [PATCH v3 3/5] iommu: Add iommu_get_domain_for_dev_locked()
 helper

On Thu, Aug 21, 2025 at 08:07:01AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@...dia.com>
> > Sent: Saturday, August 16, 2025 2:45 AM
> > 
> > On Fri, Aug 15, 2025 at 08:55:28AM +0000, Tian, Kevin wrote:
> > > > From: Nicolin Chen <nicolinc@...dia.com>
> > > > Sent: Tuesday, August 12, 2025 6:59 AM
> > > > So, iommu_get_domain_for_dev() should check the gdev flag and return
> > the
> > > > blocked domain if the flag is set. But the caller of this API could hold
> > > > the group->mutex already or not, making it difficult to add the lock.
> > > >
> > > > Introduce a new iommu_get_domain_for_dev_locked() helper to be used
> > by
> > > > those drivers in a context that is already under the protection of the
> > > > group->mutex, e.g. those attach_dev callback functions. And roll out the
> > > > new helper to all the existing IOMMU drivers.
> > >
> > > iommu_get_domain_for_dev() is also called outside of attach_dev
> > > callback functions, e.g. malidp_get_pgsize_bitmap(). and the returned
> > > info according to the attached domain might be saved in static
> > > structures, e.g.:
> > >
> > > 	ms->mmu_prefetch_pgsize = malidp_get_pgsize_bitmap(mp);
> > >
> > > would that cause weird issues when blocking domain is returned
> > > though one may not expect reset to happen at that point?
> > 
> > We aren't changing the iommu_get_domain_for_dev(). So, it should
> > be used exclusively for functions that are outside group->mutex,
> > like this one, i.e. they should still get the group->domain v.s.
> > the blocked domain.
> > 
> 
> Usually the difference between func() and func_locked() is only about
> whether the caller holds a lock. If they mean to return different
> domains, may need better naming (though I don't have a good option
> now)...

Yea, naming is tricky here :)

Perhaps it could follow a different pattern:
    iommu_dev_get_domain_for_driver(struct device *dev);

With a simple note highlighting to be used by IOMMU drivers in the
iommu callback functions like attach_dev.

Nicolin