linux-kernel - RE: [PATCH v5] modify the IO_TLB_SEGSIZE and IO_TLB_DEFAULT_SIZE configurable as flexible requirement about SW-IOMMU.

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Date:	Thu, 5 Mar 2015 08:52:59 +0000
From:	"Wang, Xiaoming" <xiaoming.wang@...el.com>
To:	Jan Beulich <JBeulich@...e.com>
CC:	"Liu@...rp2030.oracle.com" <Liu@...rp2030.oracle.com>,
	"Zhang@...rp2030.oracle.com" <Zhang@...rp2030.oracle.com>,
	"chris@...is-wilson.co.uk" <chris@...is-wilson.co.uk>,
	"david.vrabel@...rix.com" <david.vrabel@...rix.com>,
	"lauraa@...eaurora.org" <lauraa@...eaurora.org>,
	"heiko.carstens@...ibm.com" <heiko.carstens@...ibm.com>,
	"linux@...izon.com" <linux@...izon.com>,
	"Liu, Chuansheng" <chuansheng.liu@...el.com>,
	"Zhang, Dongxing" <dongxing.zhang@...el.com>,
	"takahiro.akashi@...aro.org" <takahiro.akashi@...aro.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"ralf@...ux-mips.org" <ralf@...ux-mips.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	"boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	"d.kasatkin@...sung.com" <d.kasatkin@...sung.com>,
	"pebolle@...cali.nl" <pebolle@...cali.nl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v5] modify the IO_TLB_SEGSIZE and IO_TLB_DEFAULT_SIZE
 configurable as flexible requirement about SW-IOMMU.

Dear Jan

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@...e.com]
> Sent: Thursday, March 5, 2015 4:40 PM
> To: Wang, Xiaoming
> Cc: Liu@...rp2030.oracle.com; Zhang@...rp2030.oracle.com; chris@...is-
> wilson.co.uk; david.vrabel@...rix.com; lauraa@...eaurora.org;
> heiko.carstens@...ibm.com; linux@...izon.com; Liu, Chuansheng; Zhang,
> Dongxing; takahiro.akashi@...aro.org; akpm@...ux-foundation.org; linux-
> mips@...ux-mips.org; ralf@...ux-mips.org; xen-devel@...ts.xenproject.org;
> boris.ostrovsky@...cle.com; Konrad Rzeszutek Wilk;
> d.kasatkin@...sung.com; pebolle@...cali.nl; linux-kernel@...r.kernel.org
> Subject: RE: [PATCH v5] modify the IO_TLB_SEGSIZE and
> IO_TLB_DEFAULT_SIZE configurable as flexible requirement about SW-
> IOMMU.
> 
> >>> On 05.03.15 at 04:53, <xiaoming.wang@...el.com> wrote:
> >> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@...cle.com]
> >> 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.
> 
I don't think it's suitable to accept that "force" in any position.
If we defined Format: { <int>,force,<int>,<int>}
"force" must be located in second position. 
And we add comment for each <int> also.
Every position may be defined specifically.

> Jan

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