[Xen-devel] Re: [PATCH 02/15] [swiotlb] Add swiotlb_engine structure for tracking multiple software IO TLBs.

[FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>]

On Thu, 14 Jan 2010 18:00:51 -0500
Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:

> The structure contains all of the existing variables used in
> software IO TLB (swiotlb.c) collected within a structure.
> 
> Additionally a name variable and a deconstructor (release) function
> variable is defined for API usages.
> 
> The other set of functions: is_swiotlb_buffer, dma_capable, phys_to_bus,
> bus_to_phys, virt_to_bus, and bus_to_virt server as a method to abstract
> them out of the SWIOTLB library.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
>  include/linux/swiotlb.h |   94 
> +++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 94 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index febedcf..781c3aa 100644
> --- a/include/linux/swiotlb.h
> +++ b/include/linux/swiotlb.h
> @@ -24,6 +24,100 @@ extern int swiotlb_force;
>  
>  extern void swiotlb_init(int verbose);
>  
> +struct swiotlb_engine {
> +
> +     /*
> +      * Name of the engine (ie: "Software IO TLB")
> +      */
> +     const char      *name;

Please don't add another 'layer' to the dma path. This leads to too
many indirect function calls. Some people concern about the overhead
of even the current code.

Create something like libswiotlb or whatever (as I said before) to
export functions. Then call them directly.

btw, please send swiotlb patches to lkml.

Thanks,

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