linux-kernel - Re: [PATCH 3/3] iommu/core: split mapping to page sizes as supported by the hardware

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Date:	Tue, 13 Sep 2011 12:44:33 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
CC:	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Hiroshi DOYU <Hiroshi.DOYU@...ia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	David Brown <davidb@...eaurora.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stepan Moskovchenko <stepanm@...eaurora.org>
Subject: Re: [PATCH 3/3] iommu/core: split mapping to page sizes as supported
 by the hardware

On Tue, Sep 13, 2011 at 06:34:23AM -0400, Ohad Ben-Cohen wrote:
> Hi Joerg,
> 
> On Tue, Sep 13, 2011 at 1:10 PM, Roedel, Joerg <Joerg.Roedel@....com> wrote:
> > Please split this patch into the core-change and patches for the
> > individual iommu-drivers and post this as a seperate patch-set.
> 
> But we'll be breaking bisectibility this way, no?

Not necessarily. You could implement this side-by-side with the old code
until all drivers are converted and remove the old code then. This keeps
bisectability.

> > Intel IOMMU does not support arbitrary page-sizes, afaik.
> 
> It does; besides the usual 4K it has "super page sizes" support of
> 2MB, 1GB, 512GB and 1TB.

But the value ~0xfffUL indicates support for 4k, 8k, 16k .. 2^63, no?

> 
> >> +       pr_debug("map: iova 0x%lx pa 0x%lx size 0x%lx\n", iova,
> >> +                                       (unsigned long)paddr, size);
> >
> > Please keep the debug-code in a seperate patch in your dev-tree. No need
> > for it to be merged upstream.
> 
> It's actually useful sometimes to have those around - it's off by
> default, and can be enabled only when needed (CONFIG_DYNAMIC_DEBUG).
> 
> But I don't mind removing them.

Ah right, it is just debug, so I am fine keeping it.

	Joerg

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