When the guest (firmware specifically) knows how big the address space actually is it can be used better. Some more background: https://bugzilla.redhat.com/show_bug.cgi?id=2084533 This is a RfC series exposes the information via cpuid. v2: - change fvm hint name. - better commit message. take care, Gerd Gerd Hoffmann (2): [temporary] reserve bit KVM_HINTS_PHYS_ADDRESS_SIZE_DATA_VALID [RfC] expose host-phys-bits to guest include/standard-headers/asm-x86/kvm_para.h | 3 ++- target/i386/cpu.h | 3 --- hw/i386/microvm.c | 7 ++++++- target/i386/cpu.c | 3 +-- target/i386/host-cpu.c | 5 ++++- target/i386/kvm/kvm.c | 1 + 6 files changed, 14 insertions(+), 8 deletions(-) -- 2.37.3