From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:42624) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QN6RZ-0003cW-Bv for qemu-devel@nongnu.org; Thu, 19 May 2011 12:51:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QN6RY-00028y-1X for qemu-devel@nongnu.org; Thu, 19 May 2011 12:51:25 -0400 Received: from goliath.siemens.de ([192.35.17.28]:34762) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QN6RX-00028X-M6 for qemu-devel@nongnu.org; Thu, 19 May 2011 12:51:24 -0400 Message-ID: <4DD54A89.2060907@siemens.com> Date: Thu, 19 May 2011 18:51:21 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4DD5260A.1080309@codemonkey.ws> <4DD5272F.5000003@siemens.com> <4DD52848.6030102@codemonkey.ws> <4DD52910.4080106@siemens.com> <4DD52B0E.2080604@codemonkey.ws> <4DD52BF2.2080506@redhat.com> <20110519161731.GA27310@redhat.com> <4DD5446A.6030003@siemens.com> <20110519162805.GC27310@redhat.com> <4DD545B2.70705@siemens.com> <20110519164354.GD27310@redhat.com> In-Reply-To: <20110519164354.GD27310@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] Memory API List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Avi Kivity , qemu-devel On 2011-05-19 18:43, Gleb Natapov wrote: > On Thu, May 19, 2011 at 06:30:42PM +0200, Jan Kiszka wrote: >> On 2011-05-19 18:28, Gleb Natapov wrote: >>> On Thu, May 19, 2011 at 06:25:14PM +0200, Jan Kiszka wrote: >>>> On 2011-05-19 18:17, Gleb Natapov wrote: >>>>> On Thu, May 19, 2011 at 05:40:50PM +0300, Avi Kivity wrote: >>>>>> On 05/19/2011 05:37 PM, Anthony Liguori wrote: >>>>>>> >>>>>>> So.... do you do: >>>>>>> >>>>>>> isa_register_region(ISABus *bus, MemoryRegion *mr, int priority) >>>>>>> { >>>>>>> chipset_register_region(bus->chipset, mr, priority + 1); >>>>>>> } >>>>>>> >>>>>>> I don't really understand how you can fold everything into one >>>>>>> table and not allow devices to override their parents using >>>>>>> priorities. >>>>>> >>>>>> Think of how a window manager folds windows with priorities onto a >>>>>> flat framebuffer. >>>>>> >>>>>> You do a depth-first walk of the tree. For each child list, you >>>>>> iterate it from the lowest to highest priority, allowing later >>>>>> subregions override earlier subregions. >>>>>> >>>>> And how you set those priorities in a sensible way? Why two device on a >>>>> PCI bus will want to register their memory region with anything but >>>>> highest priority? And if you let PCI subsystem to assign priorities how >>>>> it will coordinate with ISA subsystem/memory controller what priorities >>>>> to assign to get meaningful system? >>>> >>>> Priorities >default will only be used for explicit overlays, e.g. RAM >>>> over MMIO in PAM regions. Non-default priorities won't be assigned to >>>> normal PCI bars or any other device's region. >>>> >>> That does not explain who and how assign those priorities in globally >>> meaningful way. >> >> There are no global priorities. Priorities are only used inside each >> level of the memory region hierarchy to generate a resulting, flattened >> view for the next higher level. At that level, everything imported from >> below has the default prio again, ie. the lowest one. >> > Ah, so you are advocating for filtering on each level then. Because > highest level (the one that actually uses memory API) will never see > two regions with different priorities since layer bellow will flatten > the memory layout. So why do you need priorities if this is the case? > The layer that does flattening is the layer that assign priorities > anyway. See my reply to Anthony. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux