On 06/02/17 17:45, Laszlo Ersek wrote: > The patches can cause linker/loader breakage when old firmware is booted > on new QEMU. However, that's no problem (it's nothing new), the next > release of QEMU should bundle the new firmware binaries as always.
Dave made a good point (which I should have realized myself, really!), namely if you launch old fw on old qemu, then migrate the guest to a new qemu and then reboot the guest on the target host, within the migrated VM, things will break. So that makes this approach dead in the water. Possible mitigations I could think of: - Make it machine type dependent. Complicated (we don't usually bind ACPI generation to machine types) and wouldn't help existing devices. - Let the firmware negotiate these extensions. Very complicated (new fw-cfg files are needed for negotiation) and wouldn't help existing devices. So I guess I'll do what Igor and Gerd suggested: record in advance whether any pointer field narrower than 8 bytes points into a given blob, and if so, forbid allocating that blob from 64-bit address space. This should solve Ard's needs purely within the firmware. Regarding the NOACPI hint, I guess I'm dropping that. I only meant NOACPI for addressing Igor's long-standing dislike for the "ACPI SDT header probe suppression" in VMGENID (and future similar devices). But, there's no actual *technical* need to eliminate that (unlike the technical need for 64-bit blob allocations which should really be solved), so I guess it's OK to postpone NOACPI indefinitely. Self-nack for this set of sets. Thanks for the feedback, Laszlo
