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Date: Tue, 27 Feb 2024 07:40:32 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Will Deacon <will@kernel.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@android.com,
	iommu@lists.linux.dev, Christoph Hellwig <hch@lst.de>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Petr Tesarik <petr.tesarik1@huawei-partners.com>,
	Dexuan Cui <decui@microsoft.com>,
	Nicolin Chen <nicolinc@nvidia.com>,
	Michael Kelley <mhklinux@outlook.com>
Subject: Re: [PATCH v4 5/5] iommu/dma: Force swiotlb_max_mapping_size on an
 untrusted device
Message-ID: <Zd4CcL3Nnvybw2xF@infradead.org>
References: <20240221113504.7161-1-will@kernel.org>
 <20240221113504.7161-6-will@kernel.org>
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In-Reply-To: <20240221113504.7161-6-will@kernel.org>

On Wed, Feb 21, 2024 at 11:35:04AM +0000, Will Deacon wrote:
> +static size_t iommu_dma_max_mapping_size(struct device *dev)
> +{
> +	if (is_swiotlb_active(dev) && dev_is_untrusted(dev))
> +		return swiotlb_max_mapping_size(dev);

Curious: do we really need both checks here?  If swiotlb is active
for a device (for whatever reason), aren't we then always bound
by the max size?  If not please add a comment explaining it.