Guest VM kernel panic with VIRTIO_BLK with KVM

I have compiled a new linux kernel for a guest VM with CONFIG_VIRTIO_BLK=y. But it doesn’t boot and kernel panics. To kernel command line I tried passing root=/dev/vda and root=/dev/vda1 but same kernel panic comes every time. VIRTIO_NET worked fine.
But with VIRTIO_BLK we see the below kernel panic. Can someone suggest what could be going wrong?

Kernel command line is
kernel /boot/bzImage root=/dev/vda1 early_printk=serial console=hvc0 console=tty0 console=ttyS0,115200n8 divider=10 e1000.disable_vlan_offload=1 initrd /boot/initramfs.cpio

Below is a portion of GuestVM Kernel Console logs while booting up
brd: module loaded^M
vda: vda1 vda2 vda3 vda4^M
scsi0 : ata_piix^M
scsi1 : ata_piix^M
ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc180 irq 14^M
ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc188 irq 15^M

VFS: Cannot open root device “vda” or unknown-block(253,0)^M
Please append a correct “root=” boot option; here are the available partitions:^M
fd00 8388608 vda driver: virtio_blk^M
fd01 7340032 vda1 00000000-0000-0000-0000-000000000000^M
fd02 512000 vda2 00000000-0000-0000-0000-000000000000^M
fd03 535552 vda3 00000000-0000-0000-0000-000000000000^M
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(253,0)^M

Can someone suggest what could be wrong?