[PATCH] KVM: arm/arm64: Remove struct vgic_irq pending field

[Marc Zyngier]

On 23/01/17 13:39, Christoffer Dall wrote:
> One of the goals behind the VGIC redesign was to get rid of cached or
> intermediate state in the data structures, but we decided to allow
> ourselves to precompute the pending value of an IRQ based on the line
> level and pending latch state.  However, this has now become difficult
> to base proper GICv3 save/restore on, because there is a potential to
> modify the pending state without knowing if an interrupt is edge or
> level configured.
> 
> See the following post and related message for more background:
> https://lists.cs.columbia.edu/pipermail/kvmarm/2017-January/023195.html
> 
> This commit gets rid of the precomputed pending field in favor of a
> function that calculates the value when needed, irq_is_pending().
> 
> The soft_pending field is renamed to pending_latch to represent that
> this latch is the equivalent hardware latch which gets manipulated by
> the input signal for edge-triggered interrupts and when writing to the
> SPENDR/CPENDR registers.
> 
> After this commit save/restore code should be able to simply restore the
> pending_latch state, line_level state, and config state in any order and
> get the desired result.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>

I admit having lost a few brain cells looking at this patch, and I can't
prove it wrong! ;-) I like the fact that it now provides a safe
abstraction to the pending state, and that there is exactly *one* place
where line_level is evaluated.

Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>

	M.
-- 
Jazz is not dead. It just smells funny...