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SubjectRe: VMI Interface Proposal Documentation for I386, Part 5
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
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