From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 29 Jul 2008 14:53:12 +0200 From: Andrea Arcangeli Subject: Re: [PATCH] reserved-ram for pci-passthrough without VT-d capable hardware Message-ID: <20080729125312.GL11494@duo.random> References: <1214232737-21267-1-git-send-email-benami@il.ibm.com> <1214232737-21267-2-git-send-email-benami@il.ibm.com> <20080625005739.GM6938@duo.random> <20080625011808.GN6938@duo.random> <20080729121125.GK11494@duo.random> <20080729124317.GK30344@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080729124317.GK30344@one.firstfloor.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: benami@il.ibm.com, Avi Kivity , Andrew Morton , amit.shah@qumranet.com, kvm@vger.kernel.org, aliguori@us.ibm.com, allen.m.kay@intel.com, muli@il.ibm.com, linux-mm@kvack.org, tglx@linutronix.de, mingo@elte.hu List-ID: On Tue, Jul 29, 2008 at 02:43:17PM +0200, Andi Kleen wrote: > > This is a port to current linux-2.6.git of the previous reserved-ram > > patch. Let me know if there's a chance to get this acked and > > included. Anything that isn't at compile time would require much > > I still think runtime would be far better. Nobody really wants > a proliferation of more weird special kernel images. Not for the usage we're interested about but surely this would prevent distro to take advantage of the feature. The question is if distro need to take advantage of the feature in the first place instead of sticking with VT-d. 1:1 isn't secure virtualization as the guest must be trusted so it's not necessarily a good model to deploy to users that don't know exactly what they're doing. > > bigger changes just to parse the command line at 16bit realmode time > > You could always do it with kexec if you think 16bit real mode is > too hard. It's not too hard, but it'll add bloat to the 16 bit part of the boot in the bzImage. It's likely simpler than kexec and surely more user-friendly to setup for the end user. In any case, my patch does the needed bits with regard to the e820 map. An incremental patch can add the parsing of the booatloader and switch the Kconfig dependency from PHYSICAL_START to RELOCATABLE. The e820 file will then have to replace the __PHYSICAL_START define with something else and that's all. I mean it's not entirely backwards to provide a compile time smaller and simpler approach initially, and then to go where you want to go incrementally later if we're sure there's enough userbase needing 1:1. I'm not so interested to go there right now, because while this code is useful right now because the majority of systems out there lacks VT-d/iommu, I suspect this code could be nuked in the long run when all systems will ship with that, which is why I kept it all under #ifdef, and the changes to the other files outside ifdef are bugfixes needed if you want to kexec-relocate above 40m or so that should be kept. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org