Re: [PATCH v4 1/8] swiotlb: make io_tlb_default_mem local to swiotlb.c

[Philippe Mathieu-Daudé]

Hi Petr,

On 13/7/23 17:23, Petr Tesarik wrote:
> From: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx>
>
> SWIOTLB implementation details should not be exposed to the rest of the
> kernel. This will allow to make changes to the implementation without
> modifying non-swiotlb code.
>
> To avoid breaking existing users, provide helper functions for the few
> required fields.
>
> As a bonus, using a helper function to initialize struct device allows to
> get rid of an #ifdef in driver core.
>
> Signed-off-by: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx>
> ---
>   arch/arm/xen/mm.c          |  2 +-
>   arch/mips/pci/pci-octeon.c |  2 +-
>   arch/x86/kernel/pci-dma.c  |  2 +-
>   drivers/base/core.c        |  4 +---
>   drivers/xen/swiotlb-xen.c  |  2 +-
>   include/linux/swiotlb.h    | 25 +++++++++++++++++++++++-
>   kernel/dma/swiotlb.c       | 39 +++++++++++++++++++++++++++++++++++++-
>   7 files changed, 67 insertions(+), 9 deletions(-)


> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index 4e52cd5e0bdc..07216af59e93 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -110,7 +110,6 @@ struct io_tlb_mem {
>   	atomic_long_t used_hiwater;
>   #endif
>   };
> -extern struct io_tlb_mem io_tlb_default_mem;
>   
>   static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
>   {
> @@ -128,13 +127,22 @@ static inline bool is_swiotlb_force_bounce(struct device *dev)
>   
>   void swiotlb_init(bool addressing_limited, unsigned int flags);
>   void __init swiotlb_exit(void);
> +void swiotlb_dev_init(struct device *dev);
>   size_t swiotlb_max_mapping_size(struct device *dev);
> +bool is_swiotlb_allocated(void);
>   bool is_swiotlb_active(struct device *dev);
>   void __init swiotlb_adjust_size(unsigned long size);
> +phys_addr_t default_swiotlb_start(void);
> +phys_addr_t default_swiotlb_limit(void);

Usually we use start/end, base/limit, low[est]/high[est] tuples.

Possibly clearer to rename, regardless:
Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>

> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 2b83e3ad9dca..873b077d7e37 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c


> @@ -958,6 +975,26 @@ bool is_swiotlb_active(struct device *dev)
>   }
>   EXPORT_SYMBOL_GPL(is_swiotlb_active);
>   
> +/**
> + * default_swiotlb_start() - get the start of the default SWIOTLB
> + *
> + * Get the lowest physical address used by the default software IO TLB pool.
> + */
> +phys_addr_t default_swiotlb_start(void)
> +{
> +	return io_tlb_default_mem.start;
> +}
> +
> +/**
> + * default_swiotlb_limit() - get the highest address in the default SWIOTLB
> + *
> + * Get the highest physical address used by the default software IO TLB pool.

(note you describe lowest/highest).

> + */
> +phys_addr_t default_swiotlb_limit(void)
> +{
> +	return io_tlb_default_mem.end - 1;
> +}
> +
>   #ifdef CONFIG_DEBUG_FS
>   
>   static int io_tlb_used_get(void *data, u64 *val)