[Xen-devel] Re: [Xen-changelog] Create new vcpu_op() hypercall. Replaces old boot_vcpu()

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 3 Oct 2005, at 19:42, Ryan Harper wrote:

> Both do_boot_vcpu() and now VCPU_CREATE rely on domU kernel playing 
> nice
> and not making the hypercall more than has been indicated in the shared
> table when we built the domain (nr_vcpus).  Wouldn't it be better to
> have the domain creation hypercall specify the number of vcpus for a
> domain (as well as a cpumap to indicate which physical cpus are to be
> used) and alloc vcpu structures at that point leaving the vcpu_ops() to
> get context and unpause the vcpu?
>
> If I put together a patch that mode the above change, would that be
> considered?
I think there's not much in it -- allocating on demand vs. allocate at 
domain build time. I think the simplest patch would be for Xen to be 
passed a max_vcpuid or max_vcpus and apply the appropriate simple check 
at VCPUOP_create.
I'd take a patch that adds a new dom0 op to set that value 
(DOM0_SET_MAX_VCPUS or somesuch), applies the appropriate check inside 
Xen. Also that plumbs that hypercall into the Python wrapper, and adds 
a call to that command in xend (both during initial build and on 
save/restore).
 -- Keir


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