On Mon, Sep 19, 2016 at 12:51:46PM +0200, Alexander Graf wrote:

On 16.09.16 15:30, Christoffer Dall wrote:

[...]

quoted

That being said, I'm not categorically against these patches, but I
share Marc's view that we've already seen that non-vgic support had been
broken for multiple versions without anyone complaining, and without
automated testing or substantial interest in the work, the patches
really are likely to bit-rot.

I know that it's very hard to grasp from an upstream maintainer
perspective, 

pfff

but keep in mind where the bulk of execution of kernel code
lies. The average life cycle of a "stable" Linux distribution's kernel
is a few years.

So far all regressions in the user space gic code have been found within
less than 1y of the respective code release. I'd say that counts for
quite a well used feature.

The only report I can think of about this was Pavel using an upstream
kernel for in-house Samsung development on non-public hardware.

But, again, I didn't look at the patches in detail yet, I'm not
categorically against them, I will take a careful look at them like I do
with all patches on the kvmarm list.  There's a risk they'll break in
mainline unless we sort out our testing story, and it may just be
something we'll have to live with.

quoted

But I haven't even looked at the patches in detail, I was just replying
to the comment about testing.

Also keep in mind that without the architected timer support (and/or
without qemu patches than enable user space timers) the user space gic
support is pretty unusable to most people, so you obviously get less
reports.

I don't disagree with this.  I don't know what this has to do with the
part of my mail you're replying to, but I completely agree that the
current userspace irqchip support has limited value.

-Christoffer