Jason Baron <jba...@redhat.com> writes:
> On Mon, Sep 24, 2012 at 06:52:29PM +0200, Markus Armbruster wrote:
>> Jason Baron <jba...@redhat.com> writes:
>>
>> > On Fri, Sep 21, 2012 at 04:05:14PM +0200, Markus Armbruster wrote:
>> >> Jason Baron <jba...@redhat.com> writes:
>> >>
>> >> > From: Isaku Yamahata <yamah...@valinux.co.jp>
>> >> >
>> >> > Introduce a helper function which initializes the ahci port with
>> >> > ide devices.
>> >> > It will be used by q35 support.
>> >> >
>> >> > Cc: Alexander Graf <ag...@suse.de>
>> >> > Signed-off-by: Isaku Yamahata <yamah...@valinux.co.jp>
>> >> > Signed-off-by: Jason Baron <jba...@redhat.com>
>> >> > ---
>> >> > hw/ide.h | 3 +++
>> >> > hw/ide/ahci.c | 16 ++++++++++++++++
>> >> > 2 files changed, 19 insertions(+), 0 deletions(-)
>> >> >
>> >> > diff --git a/hw/ide.h b/hw/ide.h
>> >> > index 2db4079..8df872e 100644
>> >> > --- a/hw/ide.h
>> >> > +++ b/hw/ide.h
>> >> > @@ -36,4 +36,7 @@ int ide_get_bios_chs_trans(BusState *bus, int unit);
>> >> > /* ide/core.c */
>> >> > void ide_drive_get(DriveInfo **hd, int max_bus);
>> >> >
>> >> > +/* ide/ahci.c */
>> >> > +void pci_ahci_ide_create_devs(PCIDevice *pci_dev, DriveInfo
>> >> > **hd_table);
>> >> > +
>> >> > #endif /* HW_IDE_H */
>> >> > diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
>> >> > index 5ea3cad..9561210 100644
>> >> > --- a/hw/ide/ahci.c
>> >> > +++ b/hw/ide/ahci.c
>> >> > @@ -1260,3 +1260,19 @@ static void sysbus_ahci_register_types(void)
>> >> > }
>> >> >
>> >> > type_init(sysbus_ahci_register_types)
>> >> > +
>> >> > +void pci_ahci_ide_create_devs(PCIDevice *pci_dev, DriveInfo **hd_table)
>> >> > +{
>> >> > + struct AHCIPCIState *dev = DO_UPCAST(struct AHCIPCIState, card,
>> >> > pci_dev);
>> >> > + int i;
>> >> > +
>> >> > + for (i = 0; i < dev->ahci.ports; i++) {
>> >> > + /* master device only, ignore slaves */
>> >> > + if (hd_table[i * MAX_IDE_DEVS] == NULL) {
>> >> > + continue;
>> >> > + }
>> >> > + ide_create_drive(&dev->ahci.dev[i].port, 0,
>> >> > + hd_table[i * MAX_IDE_DEVS]);
>> >> > + }
>> >> > +}
>> >> > +
>> >>
>> >> Ignores odd entries in hd_table[] (MAX_IDE_DEVS is 2). Here's my
>> >> attempt at explaining why.
>> >>
>> >> -drive has parameters bus, unit, and index. index and (bus, unit) are
>> >> related in a well-known way that depends on parameter if. For if=ide,
>> >> index = bus * 2 + unit. This relationship is ABI, i.e. it cannot be
>> >> changed.
>> >>
>> >> "bus * 2 + unit" makes sense for IDE, because each IDE bus can connect
>> >> two IDE devices, "master" and "slave".
>> >>
>> >> Boards implementing IDE reject drives with (bus, unit) that make no
>> >> sense for the board's IDE controller(s). A typical board has a single
>> >> controller with two buses, which means bus > 1 get rejected.
>> >>
>> >> q35 implements AHCI instead of IDE. It connects if=ide drives to AHCI,
>> >> because that's felt to be convenient.
>> >>
>> >> An AHCI port can connect a single AHCI device, unlike an IDE bus. This
>> >> patch identifies maps -drive's bus to AHCI port number.
>> >>
>> >> PATCH 11/25 sets up argument hd_table[] as follows:
>> >>
>> >> ide_drive_get(hd, MAX_SATA_PORTS);
>> >>
>> >> This rejects bus > MAX_SATA_PORTS. It doesn't reject unit == 1. I
>> >> believe these get silently ignored. Bug or feature?
>> >>
>> >> Should we reject unit == 1 instead?
>> >>
>> >> Should we map -drive's index to AHCI port number instead?
>> >
>> > Right, so now that we have ide disks that can be attached to either the
>> > legacy ide controller or to ahci, I think we need to differentiate which
>> > controller we mean. That is, as proposed q35 is treating -drive if=ide
>> > as an ide attached to the ahci controller. I think that is broken
>> > behavior b/c we need a way to differentiate between the controllers.
>>
>> What exactly is broken?
>>
>
> I think that -drive if=ide should result in a disk attached piix3-ide.
> Not in an ide disk attached to the ahci controller (which is current q35
> bahavior, and is 'broken' b/c we don't want that to change after q35 is
> introdued). The reason being is that I think there should be an easy way
> to create an ide drive on piix3-ide, and an ide drive on the ahci
> controller. But it sounds like you don't agree with this point.
Two issues with that:
1. Why should q35 have a piix3-ide? The ICH9 southbridge provides only
SATA, so the board needs additional circuitry to provide PATA. As far
as I can tell, intel's Q35 doesn't. ICH9-based boards that do certainly
won't use a piix3-ide, because that's a *function* of the PIIX
southbridge device. It doesn't exist separately.
2. Why should we connect -drive if=ide to a slow PATA controller instead
of a perfectly servicable SATA controller?
>> > As Alexander Graf has proposed before, I think we need a -drive if=ahci
>> > introduced. In that case, I think we reject unit > 0, as you've
>> > suggested.
>>
>> Achieved by setting if_max_devs[IF_AHCI] to one. bus becomes an alias
>> for index, and unit must be zero.
>>
>> Alternatively, keep if_max_devs[IF_AHCI] zero. Swaps role of bus and
>> unit.
>>
>> Alex had if_max_devs[IF_AHCI] = 6.
>>
>> > In terms of the current q35 patch series, I think the first step would
>> > be to introduce the ahci interface type, and have hda-hdd be added with
>> > the default type for q35 of ahci. Then, we can simply fetch ahci drives
>> > of index 0-3, and populate the controller, without any of this skipping
>> > odd numbers stuff.
>> >
>> > The next step would then to add if=ahci interface to -drive.
>>
>> We discussed if=ahci at length before, without reaching consensus. I'd
>> rather not rehash the old arguments again. Instead, let's examine how
>> the command line should behave, and only then figure out how to get
>> that.
>>
>> 1. Drives created with -hd[a-d], -cdrom, or the non-option image
>> argument should connect to well-known connectors of the board's
>> preferred controller.
>>
>> For current pc, the preferred controller is piix3-ide. -hda connects
>> to its primary bus as master, -hdb as slave. -hdc connects to its
>> secondary bus as master, -hdd as slave.
>>
>> For pseries, the preferred controller is spapr-vscsi. -hda connects
>> as SCSI ID 0, -hdb as 1, and so forth.
>>
>> For s390-virtio, the preferred controller is virtio-blk-s390. -hda
>> and -hdb connect to their own virtio-blk-s390 controller, -hdc and
>> -hdd get silently ignored. Yes, that's wacky. Your current q35
>> patch is similarly wacky, as far as I can tell: -hdb and -hdd get
>> silently ignored.
>>
>> For q35, the preferred controller is ich9-ahci. I'd expect -hda to
>> connect to port 0, -hdb to port 1, and so forth.
>>
>> Below the hood, -hda is currently like -drive index=0,media=disk,
>> -hd[b-d] same with index=1..3, and -cdrom is like -drive
>> index=2,media=cdrom, independent of the board.
>>
>> It follows that -cdrom connects to the same connector as -hdc for all
>> boards. Fine for pc, but may not be as fine for some other boards.
>> You can't use both -hdc and -cdrom at the same time.
>>
>> The non-option image argument is equivalent to -hda. You can't use
>> both at the same time.
>>
>> 2. Drives created with -drive without if, index, bus, and unit connect
>> to the next unused connector of the board's preferred controller.
>>
>> If all connectors are in use, behavior currently depends on the
>> board, I think.
>>
>> 3. -drive parameters (if, index) provide more control over the connector
>> to use.
>>
>> Which controller you get for which if depends on the board. So does
>> the meaning of index. The details can get messy.
>>
>> For instance, drives with (if, index) the board doesn't support
>> sometimes get ignored silently, and sometimes get flagged as error.
>>
>> Currently, -drive without parameter if is equivalent to either if=ide
>> or if=scsi. Could be changed for new machine types.
>>
>> For q35, -drive index=0..5 should connect to ports 0..5 of the
>> board's ich9-ahci.
>>
>> 4. -drive parameters (bus, unit) are an alternate way to specify
>> parameter index. The mapping between index and (bus, unit) depends
>> on the board.
>>
>> Actually, it depends only on parameter if right now. For if=ide,
>> index = bus * 2 + unit, unit<2. For if=scsi, index = bus * 7 + unit,
>> unit < 7. For everything else, index = unit, bus = 0. We might want
>> to make it depend on the board, see commit 27d6bf40.
>>
>> For q35, we want index = bus * 6 + unit, unit<5.
>>
>> An easy way to get that is new if=ahci. Backfires when an AHCI
>> controller with a different number of ports shows up.
>>
>
> I agree with points 1-4.
>
>> We really should make the mapping between index and (bus, unit)
>> depend on the board. And then we can just as well use if=ide to
>> refer to q35's one and only IDE-like controller ich9-ahci.
>
> I agree mapping should depend on the board.
We agree on the important things then.
> But I'm not sure about using if=ide to use ich9-ahci. I'm suggesting
> that if=ide should continue to refer to piix3-ide.
Perhaps it should mean "the board's preferred ATA controller", perhaps
it should mean "the board's preferred PATA controller". Certainly
debatable.
If the latter, not necessarily piix3-ide.
