Re: [PATCH v2 3/3] iommu: dart: Add DART iommu driver

[Will Deacon <will@kernel.org>]

On Sun, Mar 28, 2021 at 09:40:09AM +0200, Sven Peter wrote:
> Apple's new SoCs use iommus for almost all peripherals. These Device
> Address Resolution Tables must be setup before these peripherals can
> act as DMA masters.
> 
> Signed-off-by: Sven Peter <sven@svenpeter.dev>
> ---
>  MAINTAINERS                      |   1 +
>  drivers/iommu/Kconfig            |  14 +
>  drivers/iommu/Makefile           |   1 +
>  drivers/iommu/apple-dart-iommu.c | 858 +++++++++++++++++++++++++++++++
>  4 files changed, 874 insertions(+)
>  create mode 100644 drivers/iommu/apple-dart-iommu.c

[...]

> +/* must be called with held domain->lock */
> +static int apple_dart_attach_stream(struct apple_dart_domain *domain,
> +				    struct apple_dart *dart, u32 sid)
> +{
> +	unsigned long flags;
> +	struct apple_dart_stream *stream;
> +	struct io_pgtable_cfg *pgtbl_cfg;
> +	int ret;
> +
> +	list_for_each_entry(stream, &domain->streams, stream_head) {
> +		if (stream->dart == dart && stream->sid == sid) {
> +			stream->num_devices++;
> +			return 0;
> +		}
> +	}
> +
> +	spin_lock_irqsave(&dart->lock, flags);
> +
> +	if (WARN_ON(dart->used_sids & BIT(sid))) {
> +		ret = -EINVAL;
> +		goto error;
> +	}
> +
> +	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
> +	if (!stream) {
> +		ret = -ENOMEM;
> +		goto error;
> +	}

Just in case you missed it, a cocci bot noticed that you're using GFP_KERNEL
to allocate while holding a spinlock here:

https://lore.kernel.org/r/alpine.DEB.2.22.394.2104041724340.2958@hadrien

Will