Re: [Xen-devel] [PATCH v3 00/26] arm64: Dom0 ITS emulation

[Julien Grall <julien.grall@xxxxxxx>]

On 31/03/2017 19:04, Andre Przywara wrote:
> Hi,
Hi Andre,

> The time I planned for the indirect device table was spent on the above two
> items, so I will write this now while the reviewers are on it.
>
> I tried to check every error return and kick out every signed int.
> Also the bug that Vijay reported has been fixed (I hope).
> While the two command line parameters are still around, the Kconfig
> options have been removed.
> I tried to separate functions between the existing VGIC and the LPI
> and ITS code parts. However there is always some connection which prevents
> a clean separation (I tried several approaches).
> I checked using the vgic_ops structure, but that feels like abuse for some
> functions, also has issues since a GICv3 and a GICv3 with ITS are not
> really separate (both could have LPIs), and the latter would always be a
> superset of the former, which duplicates code and makes a separate
> vgic_ops questionable.
There are reasons why I asked no direct call to {,v}GICv3 specific 
functions in the common code. As you may know common code is very 
generic and here to abstract the implementation of a specific GIC 
controller. It will become quickly unmaintainable if we start to do that.
Do you think the irqchip Linux maintainers will accept direct GICv3 call 
in the generic code? They will clearly say no and probably not in a very 
politely way, this is similar here.
Regarding the vgic_ops, I asked to have separate vgic ops for vGICv3 and 
vGICv3 with ITS because some code path differs. For instance we don't 
support LPIs without ITS yet. So it makes sense to avoid LPIs code to be 
called by mistake without ITS. Duplicating a vgic_ops (at max 10 lines) 
is not much compare to the potential issues.
You also seem to assume that Xen compiled with ITS will only run on 
GICv3 ITS platform. This is not true at all. The same binary can run on 
a wide range of platform.
This is not the first time I asked that. So let me be clear, I will not 
accept any call to specific functions nor #ifdef CONFIG_HAS_ITS in 
common code. It is a direct NAck from me.
Cheers,

--
Julien Grall

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