Re: [Xen-devel] [PATCH v5] modify the IO_TLB_SEGSIZE and IO_TLB_DEFAULT_SIZE configurable as flexible requirement about SW-IOMMU.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.03.15 at 04:53, <xiaoming.wang@xxxxxxxxx> wrote:
>> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
>> Sent: Thursday, March 5, 2015 3:43 AM
>> On Tue, Mar 03, 2015 at 04:11:09PM +0800, Wang Xiaoming wrote:
>> > @@ -101,13 +119,32 @@ setup_io_tlb_npages(char *str)  {
>> >    if (isdigit(*str)) {
>> >            io_tlb_nslabs = simple_strtoul(str, &str, 0);
>> > -          /* avoid tail segment of size < IO_TLB_SEGSIZE */
>> > -          io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
>> >    }
>> >    if (*str == ',')
>> >            ++str;
>> > -  if (!strcmp(str, "force"))
>> > +  if (!strncmp(str, "force", 5)) {
>> >            swiotlb_force = 1;
>> > +          str += 5;
>> > +  }
>> 
>> So the format is now:
>> 
>>      Format: { <int> | force | <int> | <int>}
>> 
>> which means I can do
>>      32,22323,force
>> 
>> Or
>>      force,32
>> 
>> Or
>>      32,force
>> 
> If I use Format: { <int>,force,<int>,<int>}
> 32,22323,force can't acceptable.
> There are three  <int>  here, if there are out of order, that will cause 
> confuse.
> Only  32,force,32323
> Or    32,,32323,2322
> Or    ,,323222,3232
> Are available.

You need to make sure that all previously valid variants are still
usable, i.e. force alone, a number alone, force,<number> and
<number>,force. How many variants you want to support with
your additions is mostly up to you; I'd recommend permitting force
in any position.

Jan


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