Re: [Qemu-devel] [RFC PATCH 14/26] ppc/xive: add MMIO handlers to the XIVE interrupt presenter model

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Jul 24, 2017 at 04:44:00PM +0200, Cédric Le Goater wrote:
> On 07/24/2017 08:35 AM, David Gibson wrote:
> > On Wed, Jul 05, 2017 at 07:13:27PM +0200, Cédric Le Goater wrote:
> >> The Thread Interrupt Management Area for the OS is mostly used to
> >> acknowledge interrupts and set the CPPR of the CPU.
> >>
> >> The TIMA is mapped at the same address for each CPU. 'current_cpu' is
> >> used to retrieve the targeted interrupt presenter object.
> >>
> >> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> > 
> > Am I right in thinking that this shoehorns the XIVE TIMA state into
> > the existing XICS ICP object.  That.. doesn't seem like a good idea.
> 
> The TIMA memory region is under the XIVE object because it is 
> unique for the system. The lookup of the ICP is simply done using 
> 'current_cpu'. The TIMA state is under the ICPState, yes, but this 
> model does not seem incorrect to me as this state contains the 
> interrupt information presented to a CPU.

Yeah, that's not the point I'm making.  My point is that the TIMA
state isn't really the same as xics ICP state.  You're squeezing one
into the other in a pretty ugly way.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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