From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Andreas_F=E4rber?= Subject: Re: [Qemu-devel] KVM call minutes 2013-01-29 - Port I/O Date: Wed, 30 Jan 2013 21:33:05 +0100 Message-ID: <51098381.8080106@suse.de> References: <871ud4gfoa.fsf@elfo.elfo> <5109065B.4060803@suse.de> <51095EA3.3000703@suse.de> <20130130202024.GE6001@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Peter Maydell , KVM devel mailing list , Juan Quintela , qemu-devel , Alexander Graf , =?ISO-8859-1?Q?Herv=E9_Poussineau?= , Gerd Hoffmann , Anthony Liguori , qemu-ppc , Alon Levy , David Gibson To: "Michael S. Tsirkin" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:37924 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752122Ab3A3UdS (ORCPT ); Wed, 30 Jan 2013 15:33:18 -0500 In-Reply-To: <20130130202024.GE6001@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Am 30.01.2013 21:20, schrieb Michael S. Tsirkin: > On Wed, Jan 30, 2013 at 06:55:47PM +0100, Andreas F=E4rber wrote: >> Am 30.01.2013 12:48, schrieb Peter Maydell: >>> On 30 January 2013 11:39, Andreas F=E4rber wrote= : >>>> Proposal by hpoussin was to move _list_add() code to ISADevice: >>>> http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg00508.html >>>> >>>> Concerns: >>>> * PCI devices (VGA, QXL) register I/O ports as well >>>> =3D> above patches add dependency on ISABus to machines >>>> -> " no mac ever had one" >>>> =3D> PCIDevice shouldn't use ISA API with NULL ISADevice >>>> * Lack of avi: Who decides about memory API these days? >>>> >>>> armbru and agraf concluded that moving this into ISA is wrong. >>>> >>>> =3D> I will drop the remaining ioport patches from above series. >>>> >>>> Suggestions on how to proceed with tackling the issue are welcome. >>> >>> How does this stuff work on real hardware? I would have >>> expected that a PCI device registering the fact it has >>> IO ports would have to do so via the PCI controller it >>> is plugged into... >>> >>> My naive don't-know-much-about-portio suggestion is that this >>> should work the same way as memory regions: each device >>> provides portio regions, >> >> One remark on "same way as memory regions", me not knowing all the g= ory >> hardware details myself. >> >> PIO often contradicts the normal MemoryRegion usage. I.e., for an MM= IO >> device you would have a continuous region from say 0xa0000000 to >> 0xa007ffff inclusive and within that region you have some kind of sp= arse >> registers. With ISA ports you often have dense overlapping ranges, s= ay, >> 0x3-0x6 byte-reads foo, while 0x4 word-write does bar. >=20 > Hmm on x86 this is what happens with cf8..cfb range registers for exa= mple. > We plan handle this ATM using memory region priorities. > Same would work for prep won't it? Hm, my point was that iiuc a MemoryRegion is per-address-range whereas for I/O ports we seem to have per-data-width mappings. Priorities would allow us to say: 0x1 - 0xff is one region 0x8-0xab is a region with higher priority but fallback for, e.g., word-access at 0xa0 to the lower-priority regio= n being unsupported today, no? I.e., the region being opaque. Having said that, for the purposes of this discussion PReP is pretty much a PC with a PowerPC CPU in it, unlike the modern CHRP machines. Andreas >> This is handled by having lists of (offset, length, size, handler) >> quadruplets and consolidating those into MemoryRegions and aliases (= cf. >> patches) that then have a validation function to check whether a >> particular access is valid and by whom it should be handled - that's >> what MemoryRegionPortio[] and similar APIs are good for. >> >> So yes, it might be possible to have a device declare its ports at >> PCIDevice or DeviceState level, but it can't be directly passed thro= ugh >> to MemoryRegion API in most cases, or conflicts would arise. At leas= t >> that was my experience with PReP. --=20 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imend=F6rffer; HRB 16746 AG N=FCrn= berg