Why does Xen kernel panic while normal kernel works fine?

Issue

• Xen kernel refuses to boot and giving kernel panic message pasted below.

  Call Trace:
   [<ffffffff80277a89>] pci_swiotlb_init+0x9/0x2d
   [<ffffffff806b1b3e>] mem_init+0x13/0x1e8
   [<ffffffff806a6a79>] start_kernel+0x189/0x224
   [<ffffffff806a61e5>] _sinittext+0x1e5/0x1eb
  
  Code: 0f 0b 68 d0 f8 4a 80 c2 a0 00 48 83 eb 80 48 8b 05 76 9e 45
  RIP  [<ffffffff8034c57d>] swiotlb_init_with_default_size+0xa0/0x19e
   RSP <ffffffff8069df40>
   <0>Kernel panic - not syncing: Fatal exception
  

Regular kernel boots fine. Tried upgrading kernel, but problem persists.