On Mon, Jan 23, 2023 at 10:00:43PM +0100, Mateusz Jończyk wrote: > W dniu 23.01.2023 o 21:33, Bjorn Helgaas pisze: > > On Sat, Jan 21, 2023 at 04:33:14PM +0100, Mateusz Jończyk wrote: > >> On some platforms, the ACPI _PRT function returns duplicate interrupt > >> routing entries. Linux uses the first matching entry, but sometimes the > >> second matching entry contains the correct interrupt vector. > >> > >> Print an error to dmesg if duplicate interrupt routing entries are > >> present, so that we could check how many models are affected. > > > > It shouldn't be too hard to use qemu to figure out whether Windows > > uses the last matching entry, i.e., treating _PRT entries as > > assignments. If so, maybe Linux could just do the same. > > > > Is anybody up for that? > > The hardware in question has a working Windows XP installation, > and I could in theory check which interrupt vector it uses - but > I think that such reverse engineering is forbidden by Windows' EULA. I'm not talking about any sort of disassembly or anything like that; just that we can observe what Windows does given the _PRT contents. You've already figured out that on your particular hardware, the _PRT has two entries, and Linux uses the first one while Windows uses the second one, right? On qemu, we have control over the BIOS and can easily update _PRT to whatever we want, and then we could boot Windows and see what it uses. But I guess maybe that wouldn't tell us anything more than what you already discovered. So my inclination would be to make Linux use the last matching entry. Bjorn
