From: Jeremy Fitzhardinge Subject: Re: [PATCH 00 of 14] swiotlb/x86: lay groundwork for xen dom0 use of swiotlb Date: Thu, 18 Dec 2008 12:09:13 -0800 Message-ID: <494AADE9.8040503@goop.org> References: <20081216203513.GA14787@elte.hu> <20081217142637V.fujita.tomonori@lab.ntt.co.jp> <4949296F.7000701@goop.org> <20081218015705Z.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Becky Bruce Cc: xen-devel@lists.xensource.com, ian.campbell@citrix.com, joerg.roedel@amd.com, x86@kernel.org, Linux Kernel Mailing List , FUJITA Tomonori , Benjamin Herrenschmidt , Ingo Molnar List-Id: xen-devel@lists.xenproject.org Becky Bruce wrote: > 32-bit powerpc needs this support - I was actually about to push a > similar set of patches. We have several processors that support 36 > bits of physical address space and do not have any iommu capability. > The rest of the kernel support for those processors is now in place, > so swiotlb is the last piece of the puzzle for that to be fully > functional. I need to take a closer look at this series to see > exactly what it's doing and how it differs from what I've been testing. > > So there is another immediate use case, and I'd really hate to see > this code duplicated. It should be entirely possible to remove the > assumption that we can save off the VA of the original buffer, which > is the thing that precludes HIGHMEM support, and still have nice > readable, maintainable code. Good, I'm glad I'm not just making things up ;) The gist of the patch is to convert all the kernel virtual addresses into struct page+offset. It's a fairly generic way to handle highmem systems, so it should work for you too. Of course, if you have a cleaner patch to achieve the same result, then we evaluate that too. J