On Thu, May 20, 2021 at 02:46:47AM +0200, BALATON Zoltan wrote: > On Wed, 19 May 2021, John Snow wrote: > > On 5/18/21 7:05 PM, BALATON Zoltan wrote: > > > On Tue, 18 May 2021, Philippe Mathieu-Daudé wrote: > > > > IDE bus depends on ISA bus for IRQ/DMA. > > > > > > > > Add an ISABus reference in PCIIDEState, and add link properties > > > > to it in the PIIX and VIA objects (which inherit PCI_IDE). > > > > > > > > Signed-off-by: Philippe Mathieu-Daudé > > > > --- > > > > include/hw/ide/pci.h |  1 + > > > > hw/ide/piix.c        | 11 ++++++++++- > > > > hw/ide/via.c         | 10 +++++++++- > > > > 3 files changed, 20 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/include/hw/ide/pci.h b/include/hw/ide/pci.h > > > > index d8384e1c422..e790722ed14 100644 > > > > --- a/include/hw/ide/pci.h > > > > +++ b/include/hw/ide/pci.h > > > > @@ -47,6 +47,7 @@ struct PCIIDEState { > > > >     PCIDevice parent_obj; > > > >     /*< public >*/ > > > > > > > > +    ISABus *isa_bus; > > > > > > I'm not sure that this belongs here. Previously we managed to remove > > > device specific fields from this structure so it's now really just > > > holds stuff related to PCI IDE (except the remaining "secondary" > > > field specific to CMD646). PCI IDE normaly has nothing to do with > > > ISA except for those south bridges that have IDE with legacy mode. > > > So this ISABus reference should be in those south bridges instead. > > > But that may need a > > > > by "those south bridges" I assume you are referring to the integrated > > PIIX and VIA controller implementations. > > Yes, those are that also have an ISA bridge so the IDE in those can use > either ISA or PCI IRQs but we probably only emulate one mode. At least > that's the case for via-ide which we have gone into great detail before and > concluded we can't cleanly switch between legacy ISA or PCI mode and the > pegasos2 needs hard coded ISA interrupts even when in PCI mode so we only > emulate that. > > Apart from that this PCI IDE is also used by CMD646 and sii3112 that are > pure PCI IDE devices without any ISA dependency so that's why I think we > should not need this ISABus here to keep this implementing PCI IDE and only > keep ISA in the south bridge models. > > > > new subclass just for this so putting it here is just avoiding > > > boilerplate of declaring new subclasses in piix and via-ide. I can > > > sympathise with that but I'd still prefer to keep it off here but I > > > wonder if there's a way to do that without subclassing and storing > > > an ISABus ref? If I understand correctly this ISABus ref is just > > > needed to get appropriate ISA irqs. But could we just store a ref to > > > those irqs > > > > It looks like it's just the IRQs, yeah. > > > > > directly so we don't need to keep the ref to the ISA bus? There's > > > > I think the idea actually is to formalize the dependency of these models > > on the ISA bus instead of hacking / faking one. I think we DO want the > > dependency. > > Right, but only piix and via depend on ISA so the dependency should be in > those not in PCI IDE in my opinion. But I don't mind too much so if it would > be too difficult to put it elsewhere I don't mind introducing this ISABus > field but we should at least look if it could be avoided first. > > > > already a qemu_irq in BMDMAState but I'm not sure how those are set > > > and if you could store an isa irq there to simplify this. I don't > > > know the details and could not detangle it by a brief look so not > > > sure it can be done but conceptually it feels better to keep PCI IDE > > > separate from ISA and let it raise either PCI irq or ISA irq as > > > needed. For that a ref to the irq should be enough and that can > > > either come from a PCI bus (which is normaly expected for PCI IDE) > > > or an ISA bridge for legacy modes. Hope it makes sense and you get > > > what I'm trying to say. (Longer term we may want to make it > > > changeable also after the device is created to allow switching > > > between legacy and PCI mode but so far we could get away without > > > emulating that so it's not a requirement just something to consider > > > when you're changing this. The real problem that prevents switching > > > modes is not irq I think but ioports and that ISA devices are not > > > configurable after creating them but that would need QOM'ifying ISA > > > emulation which probably does not worth the effort unless we come > > > across some guest that needs this.) > > > > > > Regards, > > > BALATON Zoltan > > > > > > > I assume the idea here is that PCIIDE does not technically need "ISA" to > > provide ioport access to the ATA drives, so taxonomically it's odd for > > the generic/abstract PCIIDE device to require an ISA bus. > > > > Am I understanding correctly? > > I'm not sure I understand all of the IDE emulation but in my view PCI IDE > should be independent of ISA so instead of adding a reference to an ISA bus > to PCIIDEState maybe it's enough to set the irqs used by PCI IDE to the > appropriate irq to raise which could be an ISA interrupt for the south > bridges in legacy mode or a PCI irq for PCI cards and that way we don't need > a dependency on ISABus in PCI IDE. But I'm not sure how IDE interrupts are > set so don't know if that would work so it's just an idea to avoid > introducing ISA into PCI IDE where it does not seem to belong. > > A simpler way keeping the current code may be to subclass PCI IDE in piix > and via and put the ISABus ref in those subclasses but that's more boiler > plate and the result may not be simpler so while conceptually may be cleaner > the code may be longer and harder to understand that way. So cleaning up the > interrupt handling could make it simpler and also avoid the subclasses but > that needs more work to detangle how IDE interrupts are emulated and add > some clean way to set them if that's not yet available. But I don't > completely understand what the qemu_irqs are in BMDMAState and if those > could be connected to an ISA interrupt or some more changes would be needed. I realized I don't really understand how ISA IDE and PCI IDE interact in PIIX3: - ISA IDE has well-known PIO registers that are always present? - PCI IDE has the same registers, but the BAR must be mapped and PCI IO space access must be enabled? - ISA IDE has a hardcoded ISA irq number? - PCI IDE has a normal PCI irq that is routed like any legacy PCI INTx irq? - What combinations of ISA enabled/disabled and PCI enabled/disabled need to be supported? Stefan