Description of problem:

guest BSOD if try to resize the mem to a smaller value then the than the original setting value

Version-Release number of selected component (if applicable):

kernel-5.14.0-437.el9.x86_64
qemu-kvm-8.2.0-11.el9_4.x86_64
edk2-ovmf-20240214-2.el9.noarch
seabios-bin-1.16.3-2.el9.noarch
virtio-win-prewhql-255.iso

How reproducible:
100%

Steps to Reproduce:
1. Boot a win2025（ovmf） guest with a viomem device

/usr/libexec/qemu-kvm \
-name 'avocado-vt-vm3' \
-machine q35 \
-nodefaults \
-vga std \
-device pcie-root-port,port=0x10,chassis=1,id=pci.1,bus=pcie.0,multifunction=on,addr=0x3 \
-device pcie-root-port,port=0x11,chassis=2,id=pci.2,bus=pcie.0,addr=0x3.0x1 \
-device pcie-root-port,port=0x12,chassis=3,id=pci.3,bus=pcie.0,addr=0x3.0x2 \
-device pcie-root-port,port=0x13,chassis=4,id=pci.4,bus=pcie.0,addr=0x3.0x3 \
-device pcie-root-port,port=0x14,chassis=5,id=pci.5,bus=pcie.0,addr=0x3.0x4 \
-device pcie-root-port,port=0x15,chassis=6,id=pci.6,bus=pcie.0,addr=0x3.0x5 \
-device pcie-root-port,port=0x16,chassis=7,id=pci.7,bus=pcie.0,addr=0x3.0x6 \
-device pcie-root-port,port=0x17,chassis=8,id=pci.8,bus=pcie.0,addr=0x3.0x7 \
-device virtio-net-pci,mac=9a:36:83:b6:3d:05,id=idJVpmsF,netdev=id23ZUK6,bus=pci.3 \
-netdev tap,id=id23ZUK6,vhost=on \
-blockdev node-name=file_stg2,driver=file,cache.direct=on,cache.no-flush=off,filename=win2025.qcow2,aio=threads \
-blockdev node-name=drive_stg2,driver=qcow2,cache.direct=on,cache.no-flush=off,file=file_stg2 \
-device virtio-blk-pci,id=stg2,drive=drive_stg2 \
-smp 8 \
-cpu host \
-drive id=drive_cd1,if=none,snapshot=off,aio=threads,cache=none,media=cdrom,file=/home/kvm_autotest_root/iso/ISO/Win2025/windows_server_2025_x64_dvd.iso \
-device ide-cd,id=cd2,drive=drive_cd1,bus=ide.0,unit=0 \
-cdrom /home/kvm_autotest_root/iso/windows/virtio-win-prewhql-0.1-255.iso \
-device piix3-usb-uhci,id=usb -device usb-tablet,id=input0 \
-vnc :10 \
-rtc base=localtime,clock=host,driftfix=slew \
-boot order=cdn,once=c,menu=off,strict=off \
-enable-kvm \
-qmp tcp:0:1231,server,nowait \
-monitor stdio \
-m 4G,maxmem=80G,slots=20 \
-object memory-backend-ram,id=vmem0,size=8G \
-device virtio-mem-pci,id=vm0,memdev=vmem0,node=0,requested-size=3G,bus=pci.4 \
-drive file=/usr/share/edk2/ovmf/OVMF_CODE.secboot.fd,if=pflash,format=raw,unit=0,readonly=on \
-drive file=/home/OVMF_VARS.fd,if=pflash,format=raw,unit=1 \
\

2. Shrink virtio-mem device to 1G
HMP
(qemu) qom-set vm0 requested-size 1G

Actual results:
Guest hit BSOD.

Expected results:
Guest works normally.

Other information:
1. hit this issue with win11(24H2) and win2025(ovmf)
2. for win10-64(PC)/win2019(seabios), sometimes the total mem value is not accurate