Re: [PATCH/RFC 0/2] CPU hotplug virtio driver

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Glauber de Oliveira Costa wrote:
> I'm sending a first draft of my proposed cpu hotplug driver for kvm/virtio
> The first patch is the kernel module, while the second, the userspace pci device.
>
> The host boots with the maximum cpus it should ever use, through the -smp parameter.
> Due to real machine constraints (which qemu copies), i386 does not allow for any addition
> of cpus after boot, so this is the most general way.
>
> I do however, include an "attempt_buffer" in the userspace part. It's purpose is to
> allow tools like virt-manager to set a max_cpus (-smp), and a desired number of cpus
> in their configuration files. (and AFAICT, there's is no easy way for them to tell when the
> backend driver is up and running)
>
> Other than that, it should be pretty much straightforward.
>
> Looking forward for your comments
>
>   

I would much prefer to see cpu hotplug implemented via acpi.  Such an 
implementation would work on older kernels without change, and will also 
work with other operating systems.  It isn't a high-speed interface so 
virtio doesn't buy us anything.

Linux appears to support it (CONFIG_ACPI_HOTPLUG_CPU) so all that's 
needed is the host side support (likely qemu/bios only).  Of course 
hacking on acpi is fun, if you're the kind of person than enjoys dental 
surgery.

-- 
error compiling committee.c: too many arguments to function


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