Re: [PATCH RFC v1 6/7] virtio: use io_tlb_high_mem if it is active

[Christoph Hellwig]

On Wed, Jun 08, 2022 at 05:55:52PM -0700, Dongli Zhang wrote:
>  /* Unique numbering for virtio devices. */
> @@ -241,6 +243,12 @@ static int virtio_dev_probe(struct device *_d)
>  	u64 device_features;
>  	u64 driver_features;
>  	u64 driver_features_legacy;
> +	struct device *parent = dev->dev.parent;
> +	u64 dma_mask = min_not_zero(*parent->dma_mask,
> +				    parent->bus_dma_limit);
> +
> +	if (dma_mask == DMA_BIT_MASK(64))
> +		swiotlb_use_high(parent);

The driver already very clearly communicated its addressing
requirements.  The underlying swiotlb code needs to transparently
pick the right pool.