linux-kernel - Re: [PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe path

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] [day] [month] [year] [list]

Message-ID: <20250423181813.GU1213339@ziepe.ca>
Date: Wed, 23 Apr 2025 15:18:13 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: William McVicker <willmcvicker@...gle.com>
Cc: Robin Murphy <robin.murphy@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Hanjun Guo <guohanjun@...wei.com>,
	Sudeep Holla <sudeep.holla@....com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Russell King <linux@...linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Stuart Yoder <stuyoder@...il.com>,
	Laurentiu Tudor <laurentiu.tudor@....com>,
	Nipun Gupta <nipun.gupta@....com>,
	Nikhil Agarwal <nikhil.agarwal@....com>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-pci@...r.kernel.org,
	Charan Teja Kalla <quic_charante@...cinc.com>
Subject: Re: [PATCH v2 4/4] iommu: Get DT/ACPI parsing into the proper probe
 path

On Wed, Apr 23, 2025 at 10:31:16AM -0700, William McVicker wrote:
> On 04/22/2025, Jason Gunthorpe wrote:
> > On Tue, Apr 22, 2025 at 02:55:28PM -0700, William McVicker wrote:
> > 
> > > On this note, I was looking through `of_dma_configure_id()` and am also
> > > wondering if we may hit other race conditions if the device is still being
> > > probed and the dma properties (like the coherent dma mask) haven't been fully
> > > populated? Just checking if the driver is bound, doesn't seem like enough to
> > > start configuring the DMA when async probing can happen.
> > 
> > I think the reasoning at work here is that the plugin path for a
> > struct device should synchronously setup the iommu.
> > 
> > There is enough locking there that the iommu code won't allow the
> > device plugin to continue until the iommu is fully setup under the
> > global lock.
> > 
> > The trick of using dev->driver is only a way to tell if this function
> > is being called from the driver plugin path just before starting the
> > driver, or from the iommu code just before configuring the iommu.
> > 
> > Given that explanation can you see issues with of_dma_configure_id() ?
> > 
> > Jason
> 
> I think the only concern is when a driver calls dma_set_mask_and_coherent() in
> it's probe function. If we can handle that case in an asynchrounous manner,
> then I think we are good.

You should never get to a driver probe function while iommu setup is
still concurrently running. That would be a major bug and break alot
of stuff.

Jason