Thanks,
I understand that a custom driver should react on ExitBootSevice to perform 
needed action.
Good drivers already do this.

On 30.01.2015, at 12:07, Laszlo Ersek wrote:

> On 01/30/15 09:23, Sergey Isakov wrote:
>> Dear sirs,
>> 
>> Sorry for the stupid question, I am not found an explanation.
>> If an UEFI BIOS loaded additional drivers then how to stop all of them
>> at OS started?
>> I may propose that OnExitBootService do this but
>> DxeMain.c->CoreExitBootServices () does not contain such codes.
>> So user should do this?
>> Why DxeMain will not call DisconnectAllControllers?
> 
> There's no need to disconnect controllers. Each driver's (and each
> controller's) handler for the "exiting boot services" event should abort
> pending / in-flight DMA transfers and such, but otherwise there's no
> need to release memory individually. If the memory allocations used the
> correct types throughout boot time, then the OS will repurpose
> everything it can.
> 
> Perhaps you're thinking about filesystem drivers with write caching,
> etc. IIRC, Andrew pointed out already that such drivers are unsafe
> anyway. Assume you want to reboot or poweroff the machine while at the
> UEFI shell prompt, or in the boot manager. There's no "controlled
> shutdown" option that would be usual for an OS, you just reset the
> system and that's it. The cache would be lost without ever seeing
> ExitBootServices().
> 
> (Corrections / extensions welcome, clearly. :))
> 
> Laszlo
> 
> 
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