Re: VMI Interface Proposal Documentation for I386, Part 5

[Zachary Amsden <zach@vmware.com>]

Zwane Mwaikambo wrote:
> Hello Zach,
>
> On Tue, 14 Mar 2006, Zachary Amsden wrote:
>
>   
>> It could be possible to change the semantics of the interrupt masking
>> interface in Linux, such that enable_interrupts() did just that - but did not
>> yet deliver pending IRQs.  As did restore_interrupt_mask().  This would
>> require inspection of many drivers to ensure that they don't rely on those
>> actions causing immediate interrupt delivery.  And if they did, they would
>> require a call, say, deliver_pending_irqs() to accomplish that.
>>     
>
> I think we can break these down into low level and higher level interrupt 
> enabling. Lower level tends to be call sites like exception entry, in that 
> particular case drivers aren't aware of the interrupt enable/disable 
> semantics so it's safe to enable without dispatch. Higher up is where 
> dispatch makes sense and we can closer mimick hardware.
>   

Yes, there may clearly be a benefit to having a low level / high level 
separation - say STI / PUSHF / POPF, and EnableInterrupts, 
SaveInterruptFlag, RestoreInterruptFlag.  I didn't want to do that yet, 
since it adds bulk to the interface, but there clearly is some value 
there.  And as you point out, it does save a driver audit.

Zach