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

From: Andrew Jones <ajones@ventanamicro.com>
To: Tomasz Jeznach <tjeznach@rivosinc.com>
Cc: 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: Wed, 22 May 2024 10:07:14 +0200	[thread overview]
Message-ID: <20240522-b25680db03b547123f1cd59a@orel> (raw)
In-Reply-To: <1ddb50a47c86d384157a979a7475b45f807ba81e.1715708679.git.tjeznach@rivosinc.com>

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().

Thanks,
drew

> +	list_add_rcu(&bond->list, bonds);
> +	spin_unlock(&domain->lock);
> +
> +	/* Synchronize with riscv_iommu_iotlb_inval() sequence. See comment below. */
> +	smp_mb();
> +
> +	return 0;
> +}