On Tue, Mar 01, 2016 at 03:20:59PM +0100, Andrea Bolognani wrote:
> On Tue, 2016-02-23 at 18:52 +0800, Peter Xu wrote:
> > +{ 'enum': 'GICType', 'data': [ 'gicv2', 'gicv3', 'gicv2-kvm', 'gicv3-kvm'
> > ] }
>
> Wouldn't this conflate the use of accel= and kernel_irqchip= options?
AFAIU, it's not a problem. Let me paste some lines from the original
RFC thread which explains the definition of the entries:
- gicv2: GIC version 2 without kernel IRQ chip
- gicv2-kvm: GIC version 2 with kernel IRQ chip
- gicv3: GIC version 3 without kernel IRQ chip (not supported)
- gicv3-kvm: GIC version 3 with kernel IRQ chip
(from https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg02882.html)
So... what I understand is that, we are not talking about "accel="
at all. Instead, we are talking about "kernel_irqchip=" only. Or
say, all these GIC version information we provide from QEMU does not
tell whether KVM is supported or not (for "accel=", it is provided
by another QMP message named "query-kvm"). We are only talking about
which kind of GIC we support. In our case, for each version, it
could be supported either in userspace, or in kernel.
>
> IIUC, depending on the hardware, you might find yourself in the
> following situation:
>
> accel=tcg,gic-version=3 unavailable
> accel=kvm,kernel_irqchip=off,gic-version=3 unavailable
As explained above, IIUC, both of these two "unavailable" ones
correspond to "gicv3" entry of the results.
> accel=kvm,gic-version=3 available
And this one corresponds to "gicv3-kvm" entry.
>
> so I'd expect the output to be something like
>
> [ "v2": { "tcg": true,
> "kvm-without-kernel-irqchip": true,
> "kvm": true },
> "v3": { "tcg": false,
> "kvm-without-kernel-irqchip": false,
> "kvm": true } ]
Actually, this reminded me about the "kernel_irqchip=split" case. Do
we need to consider that one? AFAIK, splitted irqchip is only used
for x86 currently. Whether ARM will possibly support splitted kernel
irqchip one day just like x86? If so, I would prefer to change the
query result layout from array to dict, like:
[ "v2": { "emulated": true,
"split": false,
"kernel": true },
"v3": { "emulated": false,
"split": false,
"kernel": true } ]
Since the matrix is big enough (2x3) to consider drop the array
format (I'd admit maybe dict is always the best one...).
Peter
>
> Since libvirt currently doesn't have support for the
> kernel_irqchip= option, it would only take the "tcg" and "kvm"
> values into account; on the other hand, if at some point
> libvirt will grow support for that option it would be able to
> retrieve all the required information.
>
> Cheers.
>
> --
> Andrea Bolognani
> Software Engineer - Virtualization Team
