On 06/17/20 15:43, Guilherme Piccoli wrote: > So, the only problem with that refactor you're proposing is the > retrocompatibility with qemu versions, as I can anticipate cases in > which newer OVMF runs with older qemu, which does not provide such > trustworth physbits info.
I don't necessarily see compat issues -- large-BAR PCI device assignment might simply stop working under those circumstances, because you could no longer use X-PciMmio64Mb, and the new way wouldn't be supported by (old) QEMU. This would indeed be a regression relative to "X-PciMmio64Mb", but that's exactly why there's an "X" in "X-PciMmio64Mb". > So, the code may be a bit complex, it'll > need to take into account this case (probably we could just rely on > the physbits "detected" by OVMF in such case, limiting PCI64 aperture > to the current 36-bits, right?). A "bit complex" is an understatement. The code is already much more complex than it should be. (And I do think that's an inherent, not accidental, complexity; it reflects the situation.) Once we have a new design, we should do the bare minimum to keep such previous usage functional that's *not* reliant on X-PciMmio64Mb. Laszlo
