Re: [PATCH v7 04/15] swiotlb: Add restricted DMA pool initialization

[Florian Fainelli <f.fainelli@xxxxxxxxx>]

On 5/17/2021 11:42 PM, Claire Chang wrote:
> Add the initialization function to create restricted DMA pools from
> matching reserved-memory nodes.
> 
> Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
> ---
>  include/linux/device.h  |  4 +++
>  include/linux/swiotlb.h |  3 +-
>  kernel/dma/swiotlb.c    | 76 +++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 82 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 38a2071cf776..4987608ea4ff 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -416,6 +416,7 @@ struct dev_links_info {
>   * @dma_pools:       Dma pools (if dma'ble device).
>   * @dma_mem: Internal for coherent mem override.
>   * @cma_area:        Contiguous memory area for dma allocations
> + * @dma_io_tlb_mem: Internal for swiotlb io_tlb_mem override.
>   * @archdata:        For arch-specific additions.
>   * @of_node: Associated device tree node.
>   * @fwnode:  Associated device node supplied by platform firmware.
> @@ -521,6 +522,9 @@ struct device {
>  #ifdef CONFIG_DMA_CMA
>       struct cma *cma_area;           /* contiguous memory area for dma
>                                          allocations */
> +#endif
> +#ifdef CONFIG_DMA_RESTRICTED_POOL
> +     struct io_tlb_mem *dma_io_tlb_mem;
>  #endif
>       /* arch specific additions */
>       struct dev_archdata     archdata;
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 216854a5e513..03ad6e3b4056 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -72,7 +72,8 @@ extern enum swiotlb_force swiotlb_force;
>   *           range check to see if the memory was in fact allocated by this
>   *           API.
>   * @nslabs:  The number of IO TLB blocks (in groups of 64) between @start and
> - *           @end. This is command line adjustable via setup_io_tlb_npages.
> + *           @end. For default swiotlb, this is command line adjustable via
> + *           setup_io_tlb_npages.
>   * @used:    The number of used IO TLB block.
>   * @list:    The free list describing the number of free entries available
>   *           from each index.
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index b849b01a446f..1d8eb4de0d01 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -39,6 +39,13 @@
>  #ifdef CONFIG_DEBUG_FS
>  #include <linux/debugfs.h>
>  #endif
> +#ifdef CONFIG_DMA_RESTRICTED_POOL
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_fdt.h>
> +#include <linux/of_reserved_mem.h>
> +#include <linux/slab.h>
> +#endif
>  
>  #include <asm/io.h>
>  #include <asm/dma.h>
> @@ -690,3 +697,72 @@ static int __init swiotlb_create_default_debugfs(void)
>  late_initcall(swiotlb_create_default_debugfs);
>  
>  #endif
> +
> +#ifdef CONFIG_DMA_RESTRICTED_POOL
> +static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
> +                                 struct device *dev)
> +{
> +     struct io_tlb_mem *mem = rmem->priv;
> +     unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
> +
> +     if (dev->dma_io_tlb_mem)
> +             return 0;
> +
> +     /*
> +      * Since multiple devices can share the same pool, the private data,
> +      * io_tlb_mem struct, will be initialized by the first device attached
> +      * to it.
> +      */
> +     if (!mem) {
> +             mem = kzalloc(struct_size(mem, slots, nslabs), GFP_KERNEL);
> +             if (!mem)
> +                     return -ENOMEM;
> +
> +             if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
> +                     kfree(mem);
> +                     return -EINVAL;

This could probably deserve a warning here to indicate that the reserved
area must be accessible within the linear mapping as I would expect a
lot of people to trip over that.

Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
-- 
Florian