Re: [PATCH v5 7/7] iommu/riscv: Paging domain support

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: Tomasz Jeznach <tjeznach@rivosinc.com>,
	Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Anup Patel <apatel@ventanamicro.com>,
	devicetree@vger.kernel.org, Conor Dooley <conor+dt@kernel.org>,
	Albert Ou <aou@eecs.berkeley.edu>,
	linux@rivosinc.com, linux-kernel@vger.kernel.org,
	Rob Herring <robh+dt@kernel.org>,
	Sebastien Boeuf <seb@rivosinc.com>,
	iommu@lists.linux.dev, Palmer Dabbelt <palmer@dabbelt.com>,
	Nick Kossifidis <mick@ics.forth.gr>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	linux-riscv@lists.infradead.org,
	Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH v5 7/7] iommu/riscv: Paging domain support
Date: Thu, 23 May 2024 12:28:10 -0300	[thread overview]
Message-ID: <20240523152810.GL69273@ziepe.ca> (raw)
In-Reply-To: <20240522-b25680db03b547123f1cd59a@orel>

On Wed, May 22, 2024 at 10:07:14AM +0200, Andrew Jones wrote:
> On Tue, May 14, 2024 at 11:16:19AM GMT, Tomasz Jeznach wrote:
> ...
> > +static int riscv_iommu_bond_link(struct riscv_iommu_domain *domain,
> > +				 struct device *dev)
> > +{
> > +	struct riscv_iommu_device *iommu = dev_to_iommu(dev);
> > +	struct riscv_iommu_bond *bond;
> > +	struct list_head *bonds;
> > +
> > +	bond = kzalloc(sizeof(*bond), GFP_KERNEL);
> > +	if (!bond)
> > +		return -ENOMEM;
> > +	bond->dev = dev;
> > +
> > +	/*
> > +	 * List of devices attached to the domain is arranged based on
> > +	 * managed IOMMU device.
> > +	 */
> > +
> > +	spin_lock(&domain->lock);
> > +	list_for_each_rcu(bonds, &domain->bonds)
> > +		if (dev_to_iommu(list_entry(bonds, struct riscv_iommu_bond, list)->dev) == iommu)
> > +			break;
> 
> We should wrap this list_for_each_rcu() in rcu_read_lock() and
> rcu_read_unlock().

Not quite this is the write side, it is holding the spinlock so it
doesn't need RCU. It should just call the normal list_for_each_entry()

Jason