From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Hackathon] Linux session notes Date: Wed, 4 Jun 2014 12:42:04 +0100 Message-ID: <538F060C.8010306@citrix.com> References: <538C99F7.3080109@citrix.com> <538F030B.1060604@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: "Xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 04/06/14 12:37, Stefano Stabellini wrote: > On Wed, 4 Jun 2014, David Vrabel wrote: >> On 04/06/14 12:11, Stefano Stabellini wrote: >>> On Mon, 2 Jun 2014, David Vrabel wrote: >>>> - Fixing m2p override. Mapping the same MFN (by two grant refs or the >>>> same) two or more times means get_user_pages() cannot find the right >>>> page() since m2p override is many-to-one. >>> >>> Did anybody proposed any ways to fix this issue? >>> We have the same problem on ARM in p2m.c and I cannot see any way to >>> solve the issue without slowing down the mfn to pfn conversion too much. >> >> I was planning to add an array of pages to the vma and use this in >> get_user_pages() (instead of the page table walk). > > That is a bit too concise. > Does that mean you are not going to fix the mfn to pfn conversion > problem and instead change the common code implementation of > get_user_pages? Yes. It's impossible to fix mfn_to_pfn() for foreign MFNs. David