Re: [Qemu-devel] [PATCH] qdev: Reset hotplugged devices

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/26/2010 03:38 AM, Isaku Yamahata wrote:
>
> 	QEMU_RESET_COLD
>    

BTW, just from a implementation perspective, I'd rather have multiple 
reset callbacks in qdev instead of having a single callback with a type 
flag.  A type flag implies that every callback has to handle all cases 
whereas with separate callbacks, if a device doesn't implement 
warm_reset we can easily default it to reset (which is a cold reset).

Regards,

Anthony Liguori

> 	Guarantee:
> 	The internal status must be same to qdev_init() + qdev_reset()
>
> 	
> warm reset
> 	system reset without cycling the supplied power.
> 	Use case:
> 	In qemu, system_reset() in main_loop(). There are many places
> 	which calls qemu_system_reset_request().
> 	Some state are retained across warm reset. Like PCIe AER, error
> 	reporting registers need to keep its contents across warm reset
> 	as OS would examine them and report it when hardware errors caused
> 	warm reset.
> 	QEMU_RESET_WARM
> 	
>
> bus reset
> 	Reset bus and devices on the bus.
> 	Bus reset is usually triggered when cold reset, warm reset and
> 	commanding the bus controller to reset the child bus.
> 	When bus reset is triggered as command to bus controller,
> 	the effect is usually same to warm reset on devices on the bus.
>
> 	Typically on parallel bus, bus reset is started by asserting
> 	a designated signal.
> 	Example: PCI RST#, ATA RESET-, SCSI RST
> 	
> 	Use case:
> 	bus reset as result of programming bus controller.
> 	Qemu is currently missing it which I'd like to fill for pci bus.
> 	ATA and SCSI could benefit from this.
> 	QEMU_RESET_WARM with bus.
> 	Guarantee:
> 	device state under the bus is same as warm reset.
>
>
> device/function reset:
> 	Reset triggered by sending reset command to a device.
> 	This is bus/device specific.
> 	There might be many reset commands whose effects are different.
> 	Example: PCI FLR, ATA DEVICE RESET command,
>                   scsi bus device reset message.
>
> 	This reset is bus specific, so it wouldn't be suitable for qdev
> 	frame work and could be handled by each bus level.
>
> 	
> hot reset:
> 	I just put it here for completeness because pcie defines hot reset.
> 	A reset propagated in-band across a Link using a Physical Layer
> 	mechanism.
> 	Qemu doesn't emulate physical layer, so we don't care it.
> 	From software point of view, hot reset has same effect to warm reset.
>
>