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

[Glauber de Oliveira Costa <gcosta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Avi Kivity wrote:
> 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.
> 
Being acpi so that fun, how can it be that virtio don't by us _anything_ ?

-------------------------------------------------------------------------
Check out the new SourceForge.net Marketplace.
It's the best place to buy or sell services for
just about anything Open Source.
http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace