Re: [Qemu-devel] Save IDEState data to files when VM shutdown

[Dr. David Alan Gilbert]

* Huaicheng Li (address@hidden) wrote:
> Hi all,
> 
> Please correct me if I’m wrong.
> 
> I made some changes to IDE emulation (add some extra structures to “struct 
> IDEState") and want to save these info to files when VM shutdowns. So I can 
> reload these info from files next time when VM starts.  According to my 
> understanding, one IDEState structure is corresponding to one disk for VM and 
> all available drives are probed/initialised by ide_init2() in hw/ide.c (I 
> used qemu v0.11) during VM startup. It seemed that IDEState structure are 
> saved to QEMUFile structure via pci_ide_save(), but I can only trace up to 
> register_savevm(), where pci_ide_save() is registered as a callback. I can’t 
> find where exactly this function starts execution or being called.  My 
> questions are: 

Version 0.11 is *ancient* - please start with something newer; pci_ide_save was 
removed 6 years ago.

> (1). Does QEMUFile structure represent a running VM instance, through which I 
> can access the IDE drive (struct IDEState) pointers ?
> 
> (2). When does qemu execute pci_ide_save()? 

QEMUFile is part of the migration code; it forms a stream of data containing
all of the device and RAM State during migration.  See savevm.c for what drives
this (in migration/savevm.c in modern qemu).
Extracting the state of one device from the stream isn't that easy.

> (3). How does qemu handle VM shutdown? It seems ACPI event is sent to VM so 
> guest OS will shutdown in the way like real OS running on real hardware. But 
> how and where does qemu exactly handle this? I think I need to add my codes 
> here. 

I don't know the detail of that; I suggest following
the code from qemu_system_powerdown.

Why are you trying to save the state during shutdown?

Dave

> 
> Any hints, suggestions would be appreciated. Thanks.
> 
> Huaicheng Li
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK