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Re: [Qemu-devel] allocation zone extensions for the firmware linker/load
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] allocation zone extensions for the firmware linker/loader |
Date: |
Mon, 5 Jun 2017 19:02:00 +0300 |
On Sat, Jun 03, 2017 at 09:36:23AM +0200, Laszlo Ersek wrote:
> 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.
This last option *shouldn't* be complicated. If it is something's wrong.
Maybe we made a mistake when we added etc/smi/*features*.
It's not too late to move these to etc/*features* for new
machine types if we want to and if you can do the firmware
work. Then you'd just take out a bit and be done with it.
I don't insist on doing the ACPI thing now but I do think
infrastructure for negotiating extensions should be there.
--
MST
- [Qemu-devel] [edk2 PATCH 1/3] OvmfPkg/AcpiPlatformDxe: rename BLOB.HostsOnlyTableData to BLOB.Releasable, (continued)