Stefan Hajnoczi <stefa...@redhat.com> writes: > On Tue, Apr 27, 2021 at 02:02:27PM -0400, John Snow wrote: >> On 4/27/21 1:54 PM, 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. >> > >> > Regards, >> > >> > Phil. >> > >> >> It sounds complicated. In the meantime, I think I am favor of taking >> Thomas's patch because it merely adds some error routing to allow us to >> avoid a crash. The core organizational issues of the IDE device(s) will >> remain and can be solved later as needed. > > The approach in this patch is okay but we should keep in mind it only > solves piix3-ide. ISA provides a non-qdev backdoor API and there may be > more instances of this type of bug. > > A qdev fix would address the root cause and make it possible to drop the > backdoor API, but that's probably too much work for little benefit.
What do you mean by backdoor API? Global @isabus?
