> -----Original Message----- > From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] > Sent: Wednesday, July 21, 2010 12:59 PM > To: Shilimkar, Santosh > Cc: stepanm@xxxxxxxxxxxxxx; linux-arch@xxxxxxxxxxxxxxx; > dwalker@xxxxxxxxxxxxxx; mel@xxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; FUJITA Tomonori; linux-mm@xxxxxxxxx; > andi@xxxxxxxxxxxxxx; Zach Pfeffer; Michael Bohan; Tim HRM; linux- > omap@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > ebiederm@xxxxxxxxxxxx > Subject: Re: [RFC 1/3 v3] mm: iommu: An API to unify IOMMU, CPU and device > memory management > > On Wed, Jul 21, 2010 at 11:19:58AM +0530, Shilimkar, Santosh wrote: > > > -----Original Message----- > > > From: linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:linux-arm- > > > kernel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Russell King - ARM > Linux > > > Sent: Wednesday, July 21, 2010 4:00 AM > > > To: stepanm@xxxxxxxxxxxxxx > > > Cc: linux-arch@xxxxxxxxxxxxxxx; dwalker@xxxxxxxxxxxxxx; mel@xxxxxxxxx; > > > linux-arm-msm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; FUJITA > > > Tomonori; linux-mm@xxxxxxxxx; andi@xxxxxxxxxxxxxx; Zach Pfeffer; > Michael > > > Bohan; Tim HRM; linux-omap@xxxxxxxxxxxxxxx; linux-arm- > > > kernel@xxxxxxxxxxxxxxxxxxx; ebiederm@xxxxxxxxxxxx > > > Subject: Re: [RFC 1/3 v3] mm: iommu: An API to unify IOMMU, CPU and > device > > > memory management > > ************************************************************************* > > > This is difficult to achieve without remapping kernel memory using L2 > > > page tables, so we can unmap pages on 4K page granularity. That's > > > going to increase TLB overhead and result in lower system performance > > > as there'll be a greater number of MMU misses. > ************************************************************************* > > > > However, one obvious case would be to use highmem-only pages for > > > remapping - but you then have to ensure that those pages are never > > > kmapped in any way, because those mappings will fall into the same > > > unpredictable category that we're already trying to avoid. This > > > may be possible, but you'll have to ensure that most of the system > > > RAM is in highmem - which poses other problems (eg, if lowmem gets > > > low.) > > > > Why can't we consider an option of removing the old mappings when > > we need to create new ones with different attributes as suggested > > by Catalin on similar thread previously. This will avoid the duplicate > > mapping with different attributes issue on newer ARMs. > > See the first paragraph which I've highlighted above. > Sorry about missing that para Russell. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
