Re: [Xen-devel] [PATCH v4] modify the IO_TLB_SEGSIZE and IO_TLB_DEFAULT_SIZE configurable as flexible requirement about SW-IOMMU.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.02.15 at 07:51, <xiaoming.wang@xxxxxxxxx> wrote:
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3438,10 +3438,12 @@ bytes respectively. Such letter suffixes can also be 
> entirely omitted.
>                       it if 0 is given (See Documentation/cgroups/memory.txt)
>  
>       swiotlb=        [ARM,IA-64,PPC,MIPS,X86]
> -                     Format: { <int> | force }
> +                     Format: { <int> | force | <int> | <int>}
>                       <int> -- Number of I/O TLB slabs
>                       force -- force using of bounce buffers even if they
>                                wouldn't be automatically used by the kernel
> +                     <int> -- Maximum allowable number of contiguous slabs 
> to map
> +                     <int> -- The size of SW-MMU mapped.

This makes no sense - the new numbers added aren't position
independent (nor were the previous <int> and "force").

Also you are (supposedly) removing all uses of
IO_TLB_DEFAULT_SIZE, yet you don't seem to remove the
definition itself.

Finally - are arbitrary numbers really okay for the newly added
command line options? I.e. shouldn't you add some checking of
their validity?

Jan


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