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From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: beckyb@kernel.crashing.org
Cc: tony.luck@intel.com, linux-ia64@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, fujita.tomonori@lab.ntt.co.jp,
	linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 04/15] swiotlb: remove unnecessary swiotlb_bus_to_virt
Date: Tue, 14 Jul 2009 14:08:47 +0900	[thread overview]
Message-ID: <20090714140805G.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <5E909C02-3FA2-4BEB-8C73-F4E4A5A404BF@kernel.crashing.org>

On Mon, 13 Jul 2009 21:17:21 -0500
Becky Bruce <beckyb@kernel.crashing.org> wrote:

> 
> On Jul 9, 2009, at 8:04 PM, FUJITA Tomonori wrote:
> 
> > swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and
> > phys_to_virt instead.
> 
> phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on  
> ppc.  In most of the uses in this file, it doesn't matter, as the  
> iotlb buffers themselves are alloc'd out of lowmem,

Right,

> but the  
> dma_mark_clean() calls could happen on a highmem addr.  Currently, on  
> powerpc, dma_mark_clean() doesn't do anything, so it isn't a  
> functional problem.

Oops, I overlooked this. However, as you said, this is not a problem
with the current code.


>  I'm fine with the bulk of this patch, because in  
> reality, if I need to do something with a virtual address of a highmem  
> page, I have to get a kmap for the page.  So the existing  
> swiotlb_bus_to_virt isn't really helping.
> 
> What is dma_mark_clean used for?  Could it be made to take a paddr,  
> and let the implementation deal with making sure there's a valid vaddr  
> for the actual "clean" operation?

I think that it's IA64's optimization (it's a NULL function on X86
like POWERPC). It's defined in arch/ia64/mm/init.c. Looks like POWERPC
could use this optimization, I guess.

dma_mark_clean() just modifies the page flag (what it needs is struct
page) so I think that we can make it take a paddr.


> I'd also like to see a comment with swiotlb_virt_to_bus() that notes  
> that it should only be called on addresses in lowmem.

Ok, I'll do.


Thanks,

  reply	other threads:[~2009-07-14  5:09 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-10  1:04 [00/15] swiotlb cleanup FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 01/15] swiotlb: remove unused swiotlb_alloc_boot() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 02/15] swiotlb: remove unused swiotlb_alloc() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 03/15] swiotlb: remove swiotlb_arch_range_needs_mapping FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 04/15] swiotlb: remove unnecessary swiotlb_bus_to_virt FUJITA Tomonori
2009-07-14  2:17   ` Becky Bruce
2009-07-14  5:08     ` FUJITA Tomonori [this message]
2009-07-16  3:40     ` Benjamin Herrenschmidt
2009-07-10  1:04 ` [PATCH 05/15] x86: add dma_capable() to replace is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 06/15] x86: replace is_buffer_dma_capable() with dma_capable FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 07/15] ia64: add dma_capable() to replace is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 08/15] powerpc: " FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 09/15] swiotlb: use dma_capable() FUJITA Tomonori
2009-07-10  1:04 ` [PATCH 10/15] powerpc: remove unncesary swiotlb_arch_address_needs_mapping FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 11/15] remove is_buffer_dma_capable() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 12/15] x86, IA64, powerpc: add phys_to_dma() and dma_to_phys() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 13/15] swiotlb: use phys_to_dma and dma_to_phys FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 14/15] powerpc: remove unused swiotlb_phys_to_bus() and swiotlb_bus_to_phys() FUJITA Tomonori
2009-07-10  1:05 ` [PATCH 15/15] x86: " FUJITA Tomonori
2009-07-10  5:12 ` [00/15] swiotlb cleanup Ingo Molnar
2009-07-10  5:35   ` FUJITA Tomonori
2009-07-10 14:02     ` Ian Campbell
2009-07-13  4:20       ` FUJITA Tomonori
2009-07-13  9:40         ` Ian Campbell
2009-07-13  9:53           ` FUJITA Tomonori
2009-07-13 10:05             ` Ian Campbell
2009-07-10 14:01   ` Ian Campbell
2009-07-10 14:12     ` Ingo Molnar
2009-07-13  4:20       ` FUJITA Tomonori
2009-07-13  9:16         ` FUJITA Tomonori
2009-07-18 10:41           ` Ingo Molnar
2009-07-14  3:13   ` Becky Bruce
2009-07-15 20:24     ` Becky Bruce

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