virtio: use virtio_device_ready() in virtio_device_restore()

Summary

In the Linux kernel, the following vulnerability has been resolved: virtio: use virtio_device_ready() in virtio_device_restore() After waking up a suspended VM, the kernel prints the following trace for virtio drivers which do not directly call virtio_device_ready() in the .restore: PM: suspend exit irq 22: nobody cared (try booting with the "irqpoll" option) Call Trace: <IRQ> dump_stack_lvl+0x38/0x49 dump_stack+0x10/0x12 __report_bad_irq+0x3a/0xaf note_interrupt.cold+0xb/0x60 handle_irq_event+0x71/0x80 handle_fasteoi_irq+0x95/0x1e0 __common_interrupt+0x6b/0x110 common_interrupt+0x63/0xe0 asm_common_interrupt+0x1e/0x40 ? __do_softirq+0x75/0x2f3 irq_exit_rcu+0x93/0xe0 sysvec_apic_timer_interrupt+0xac/0xd0 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch_cpu_idle+0x12/0x20 default_idle_call+0x39/0xf0 do_idle+0x1b5/0x210 cpu_startup_entry+0x20/0x30 start_secondary+0xf3/0x100 secondary_startup_64_no_verify+0xc3/0xcb </TASK> handlers: [<000000008f9bac49>] vp_interrupt [<000000008f9bac49>] vp_interrupt Disabling IRQ #22 This happens because we don't invoke .enable_cbs callback in virtio_device_restore(). That callback is used by some transports (e.g. virtio-pci) to enable interrupts. Let's fix it, by calling virtio_device_ready() as we do in virtio_dev_probe(). This function calls .enable_cts callback and sets DRIVER_OK status bit. This fix also avoids setting DRIVER_OK twice for those drivers that call virtio_device_ready() in the .restore.