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Re: [Qemu-devel] [RFC PATCH v3 01/10] hw: arm_gic: Fix gic_set_irq handl

From: Peter Maydell
Subject: Re: [Qemu-devel] [RFC PATCH v3 01/10] hw: arm_gic: Fix gic_set_irq handling
Date: Thu, 28 Nov 2013 17:43:54 +0000

On 28 November 2013 16:17, Peter Maydell <address@hidden> wrote:
> On 19 November 2013 06:18, Christoffer Dall <address@hidden> wrote:
> So I think this is a correct change in the sense that
> it's fixing the behaviour of this function. However
> we seem to get our pending behaviour for level triggered
> interrupts wrong in several places:
>  * here
>  * gic_acknowledge_irq (which you fix in a later patch)
>  * gic_complete_irq, which currently says "enabled
>    level triggered still-raised interrupts should be
>    remarked as pending"
> This feels to me like a cluster of errors which have come
> from somebody's misreading of the spec and which probably
> combine to produce a coherent not-too-far-from-correct
> result, and which we should therefore fix all at once rather
> than only partially.

The other possibility is that it's a correct implementation
of 11MPCore GIC semantics -- the documentation of the
11MPCore definitely says that level triggered interrupts
go from Pending to Active and can't be Active+Pending
unless software messes with the GIC state. So either
the docs are actively wrong for 11MPCore or it behaves
differently from GICv1 and v2 here (my guess would be
the latter, in which case we need to support both flavours).

-- PMM

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