From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: R/W HG memory mappings with kvm? Date: Wed, 26 Aug 2009 13:22:38 +0300 Message-ID: <4A950CEE.1080402@redhat.com> References: <5f370d430907051541o752d3dbag80d5cb251e5e4d00@mail.gmail.com> <5f370d430907081501m60064c7dp23ebd4153c9050f1@mail.gmail.com> <5f370d430907262256rd7f9fdalfbbec1f9492ce86@mail.gmail.com> <4A6DBE54.3080609@cs.ualberta.ca> <5f370d430907271432y5283c2cat7673efeed0febe20@mail.gmail.com> <4A6EBCB3.4080804@redhat.com> <5f370d430907281606j77f0c1a6j5feb081daca187ff@mail.gmail.com> <5f370d430908122107j15acd2c7i96d476e69032fadd@mail.gmail.com> <4A8BEC92.6070105@redhat.com> <5f370d430908231459q4c8cfe3j62c49e33a160ab71@mail.gmail.com> <4A921D3C.6020809@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Cam Macdonell , "kvm@vger.kernel.org list" , Marcelo Tosatti , Chris Wright To: Stephen Donnelly Return-path: Received: from mx1.redhat.com ([209.132.183.28]:10368 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756772AbZHZKWk (ORCPT ); Wed, 26 Aug 2009 06:22:40 -0400 In-Reply-To: <4A921D3C.6020809@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/24/2009 07:55 AM, Avi Kivity wrote: > On 08/24/2009 12:59 AM, Stephen Donnelly wrote: >> On Thu, Aug 20, 2009 at 12:14 AM, Avi Kivity wrote: >>> On 08/13/2009 07:07 AM, Stephen Donnelly wrote: >>>> npages = get_user_pages_fast(addr, 1, 1, page); returns -EFAULT, >>>> presumably because (vma->vm_flags& (VM_IO | VM_PFNMAP)). >>>> >>>> It takes then unlikely branch, and checks the vma, but I don't >>>> understand what it is doing here: pfn = ((addr - vma->vm_start)>> >>>> PAGE_SHIFT) + vma->vm_pgoff; >>> It's calculating the pfn according to pfnmap rules. >> From what I understand this will only work when remapping 'main >> memory', e.g. where the pgoff is equal to the physical page offset? >> VMAs that remap IO memory will usually set pgoff to 0 for the start of >> the mapping. > > If so, how do they calculate the pfn when mapping pages? kvm needs to > be able to do the same thing. Maybe the simplest thing is to call vma->vm_ops->fault here. Marcelo/Chris? Context is improving gfn_to_pfn() on the mmio path. -- error compiling committee.c: too many arguments to function