From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrea Arcangeli Subject: Re: [PATCH 1/1] direct mmio for passthrough - kernel part Date: Wed, 2 Apr 2008 00:22:51 +0200 Message-ID: <20080401222251.GC19189@duo.random> References: <1207050734-13166-1-git-send-email-benami@il.ibm.com> <1207050734-13166-2-git-send-email-benami@il.ibm.com> <47F238D8.7040608@qumranet.com> <47F249C3.6000300@codemonkey.ws> <47F26AD2.8000406@qumranet.com> <47F27D31.5050604@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, allen.m.kay@intel.com, benami@il.ibm.com, Avi Kivity To: Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <47F27D31.5050604@codemonkey.ws> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org On Tue, Apr 01, 2008 at 01:21:37PM -0500, Anthony Liguori wrote: > return a page, not a HPA. I haven't looked too deeply yet, but my > suspicion is that to properly support mapping in VM_IO pages will require > some general refactoring since we always assume that a struct page exists > for any HPA. Yes, that was potentially problem for reserved _ram_ pages too, as it isn't guaranteed that memmap_t (old days nomenclature) will exist for physical addresses not defined as ram in the e820 map (to make it work without VT-d I have to reserve the ram in the host at the e820 map parsing time). If the memmap will not exist for the reserved ram physical range, the pfn_valid() will fail at runtime in kvm and the bad_page will generate a graceful emulation failure, so it's very safe. But once we handle direct memslots for mmio regions, the reserved ram will better stop depending on the memmap too. ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace