On Tue, Apr 27, 2021 at 07:54:21PM +0200, Philippe Mathieu-Daudé wrote: > On 4/27/21 7:16 PM, John Snow wrote: > > On 4/27/21 9:54 AM, Stefan Hajnoczi wrote: > >> I suggest fixing this at the qdev level. Make piix3-ide have a > >> sub-device that inherits from ISA_DEVICE so it can only be instantiated > >> when there's an ISA bus. > >> > >> Stefan > > > > My qdev knowledge is shaky. Does this imply that you agree with the > > direction of Thomas's patch, or do you just mean to disagree with Phil > > on his preferred course of action? > > My understanding is a disagreement to both, with a 3rd direction :) > > I agree with Stefan direction but I'm not sure (yet) that a sub-device > is the best (long-term) solution. I guess there is a design issue with > this device, and would like to understanding it first. > > IIUC Stefan says the piix3-ide is both a PCI and IDE device, but QOM > only allow a single parent. Multiple QOM inheritance is resolved as > interfaces, but PCI/IDE qdev aren't interfaces, rather abstract objects. > So he suggests to embed an IDE device within the PCI piix3-ide device. > > My view is the PIIX is a chipset that share stuffs between components, > and the IDE bus belongs to the chipset PCI root (or eventually the > PCI-ISA bridge, function #0). The IDE function would use the IDE bus > from its root parent as a linked property. > My problem is currently this device is user-creatable as a Frankenstein > single PCI function, out of its chipset. I'm not sure yet this is a > dead end or I could work something out.
Kevin and Paolo previously pointed out that piix3-ide is sometimes used with the Q35 machine type. The user-creatable piix3-ide device needs to be deprecated before it can be dropped. That's a long process that cannot fix the current crash any time soon. I do support deprecating the user-creatable piix3-ide device in favor of a proper Q35 Legacy IDE implementation. The main problem is this involves a bunch of work and I'm not sure who would do it (the payoff is not very high). Stefan
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