[PATCH-SERIES qemu-server 0/4] cpu config: warn that OVMF might limit phys-bits to 40 without pdpe1gb CPU flag

Fiona Ebner
2026-03-23T13:29:03Z

OVMF limits phys-bits to 40 if no 1 GiB pages are available. When
built in debug mode, OVMF logs a debug message about this. But
otherwise, there is no user-visible log of this happening.

In practice, VMs with a lot of memory or VMs with GPU passthrough with
a lot of vRAM might not boot when the pdpe1gb CPU flag is not present.
In particular, this is the case for the built-in x86-64-vX models that
are based on the qemu64 model as well as the backend default kvm64.

It can't be expected that Proxmox VE users check the EDK II source
code to figure this out, so log a warning. The warning is limited to
CPU models based on the qemu64 and kvm64 models, since checking for
other models would require the CPU model expansion which is currently
not cheap to get. This should cover most problematic scenarios.

qemu-server:

Fiona Ebner (4):
cpu config: split resolve_cpu_flags() function
move get_host_phys_address_bits() to helpers module
cpu config: get cpu options: avoid shadowing $conf variable
cpu config: warn that OVMF might limit phys-bits to 40 without pdpe1gb
CPU flag

src/PVE/QemuServer/CPUConfig.pm | 43 ++++++++++++++++++++++++----
src/PVE/QemuServer/Helpers.pm | 18 ++++++++++++
src/PVE/QemuServer/Memory.pm | 23 ++-------------
src/test/run_config2command_tests.pl | 11 +++++--
4 files changed, 67 insertions(+), 28 deletions(-)

Summary over all repositories:
4 files changed, 67 insertions(+), 28 deletions(-)

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