On 25/04/2024 22.56, Philippe Mathieu-Daudé wrote:
Hi Thomas,
On 25/4/24 20:43, Thomas Huth wrote:
For downstream versions of QEMU, we'd like to be able to compile QEMU
without the FDC code included (since it's not required for modern VMs
anymore and the FDC code has rather a bad reputation, see the VENOM CVE).
IIRC you still need to keep the i440fx+piix machine DS due to
migration compatibility, right?
Are you able to migrate a VM booted with FDC to a non-FDC one?
Migration from a machine with FDC to one without is likely not possible. But
that's also not the purpose of this series. It's about having the
possibility to build a QEMU binary without FDC at all in case you don't have
to support old machine types with FDC anymore.
The q35 machine can already be instantiated without FDC, but for being
able to link a binary without the FDC code, the Kconfig file needs some
tweaks and there are two spots in the pc code that directly call functions
from the FDC code - those need to be disabled via #ifdefs.
Is it useful to you to have q35 without FDC but i440fx+piix with?
Or are you removing it from i440fx+piix due to shared code with q35?
I think it might get useful.
Thomas
