From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [RFC] [VTD][patch 1/3] vt-d support for pci passthrough: kvm-vtd--kernel.patch Date: Wed, 07 May 2008 14:22:16 -0500 Message-ID: <48220168.3050907@codemonkey.ws> References: <1FE6DD409037234FAB833C420AA843EC01438CB3@orsmsx424.amr.corp.intel.com> <4820F845.3080704@codemonkey.ws> <1FE6DD409037234FAB833C420AA843EC0147C07F@orsmsx424.amr.corp.intel.com> <48210C51.7090206@codemonkey.ws> <4821434E.20504@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, Chris Wright , "Kay, Allen M" , Ben-Ami Yassour1 , Andrea Arcangeli To: Avi Kivity Return-path: In-Reply-To: <4821434E.20504@qumranet.com> 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 Avi Kivity wrote: > Anthony Liguori wrote: > > >>> What should be done for unmodified guest where there is no PV driver in >>> the guest? Would a call to mlock() from >>> qemu/hw/pci-passthrough.c/add_pci_passthrough_device() a reasonable >>> thing to do? >>> >> >> Yup. The idea is to ensure that the memory is always present, >> without necessarily taking a reference to it. This allows for memory >> reclaiming which should allow for things like NUMA page migration. >> We can't swap of course but that doesn't mean reclaimation isn't useful. >> > > I don't think we can do page migration with VT-d. You need to be able > to detect whether the page has been changed by dma after you've copied > it but before you changed the pte, but VT-d doesn't allow that AFAICT. Hrm, I would have to look at the VT-d but I suspect you're right. That's unfortunate. That means mlock() isn't sufficient. It also means that the VMAs can't be updated while the guest is running. Is there any way to lock a vma region such that things like madvise/mmap(MAP_FIXED) will always fail? Regards, Anthony Liguori ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone