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

["Wang, Xiaoming" <xiaoming.wang@xxxxxxxxx>]

Dear Jan

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, February 17, 2015 6:09 PM
> To: Wang, Xiaoming
> Cc: chris@xxxxxxxxxxxxxxxxxx; david.vrabel@xxxxxxxxxx;
> lauraa@xxxxxxxxxxxxxx; heiko.carstens@xxxxxxxxxx; linux@xxxxxxxxxxx;
> Liu, Chuansheng; Zhang, Dongxing; takahiro.akashi@xxxxxxxxxx;
> akpm@xxxxxxxxxxxxxxxxxxxx; linux-mips@xxxxxxxxxxxxxx; ralf@linux-
> mips.org; xen-devel@xxxxxxxxxxxxxxxxxxxx; boris.ostrovsky@xxxxxxxxxx;
> konrad.wilk@xxxxxxxxxx; d.kasatkin@xxxxxxxxxxx; pebolle@xxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH v4] modify the IO_TLB_SEGSIZE and
> IO_TLB_DEFAULT_SIZE configurable as flexible requirement about SW-
> IOMMU.
> 
> >>> 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").
> 
Use ","  can separate them one by one.
We do it at lib/swiotlb.c
> Also you are (supposedly) removing all uses of IO_TLB_DEFAULT_SIZE, yet
> you don't seem to remove the definition itself.
> 
I have change all uses of IO_TLB_DEFAULT_SIZE to io_tlb_default_size in 
lib/swiotlb.c
> Finally - are arbitrary numbers really okay for the newly added command line
> options? I.e. shouldn't you add some checking of their validity?
> 
I have validity these code is OK.
Example:
BOARD_KERNEL_CMDLINE += swiotlb=, ,512,268435456
Io_tlb_segsize has been changed from 128 to 512
Io_tlb_default_size has been changed from 64M to 268435456  (256M)

> Jan
Xiaoming.


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