Description of problem:

Total mem size sometimes is not accurate after resize virtio-mem device

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

kernel-5.14.0-526.el9.x86_64
qemu-kvm-9.1.0-1.el9.x86_64
edk2-ovmf-20240524-8.el9.noarch
seabios-bin-1.16.3-2.el9.noarch
virtio-win-prewhql-266.iso

How reproducible:
100%

Steps to Reproduce:
1. Boot a win2019(seabios+q35) guest with a viomem device

/usr/libexec/qemu-kvm \
-name 'win2019' \
-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 \
-blockdev node-name=file_stg1,driver=file,cache.direct=on,cache.no-flush=off,filename=win2019-64-virtio.qcow2,aio=threads \
-blockdev node-name=drive_stg1,driver=qcow2,cache.direct=on,cache.no-flush=off,file=file_stg1 \
-device virtio-blk-pci,id=stg1,drive=drive_stg1,bus=pci.8,addr=0x0,bootindex=0 \
-device virtio-net-pci,mac=9a:36:83:b6:3d:05,id=idJVpmsF,netdev=id23ZUK6,bus=pci.3 \
-netdev tap,id=id23ZUK6,vhost=on \
-smp 8 \
-cpu 'Skylake-Server',hv_stimer,hv_synic,hv_vpindex,hv_reset,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time,hv-tlbflush,+kvm_pv_unhalt \
-cdrom /home/kvm_autotest_root/iso/windows/virtio-win-prewhql-0.1-266.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=1G,bus=pci.4 \

2. Resize virtio-mem device, grow and shrink

(qemu) qom-set vm0 requested-size 6G
(qemu) qom-set vm0 requested-size 2G

3.Check memory device in hmp and memory status inside guest

(qemu) info memory-devices
Memory device [virtio-mem]: "vm0"
memaddr: 0x180000000
node: 0
requested-size: 2147483648
size: 2680160256
max-size: 8589934592
block-size: 2097152
memdev: /objects/vmem0

Actual results:
Total mem size show 6.5G

Expected results:
Total mem size should be 6.0G

Other information:
1. Not related guests.
2. After reboot the guest, mem size change to expected size.