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Re: [libvirt] [Patch V2] Fix initialization of current vcpus in libxl driver



On 05/24/2011 11:22 AM, Jim Fehlig wrote:
> The cur_vcpus member of struct libxl_domain_build_info was incorrectly
> initialized to the number of vcpus, when it should have been interpreted
> as a bitmap, where bit X corresponds to online/offline status of vcpuX.
> 
> To complicate matters, cur_vcpus is an int, so only 32 vcpus can be
> set online.  Add a check to ensure vcpus does not exceed this limit.
> 
> V2: Eric Blake noted a compilation pitfal when '1 << 32' on an int.

If you keep the V2 message in your commit log, then s/pitfal/pitfall/
(personally, I tend to drop V2 messages when pushing - they are handy
during review to point out what to look for, but once it is part of
history, I no longer care how many versions it took to get to the final
pushed version).

>     Account for vcpus == 32.

> +     * as an int, but its' semantic is a bitmap of online vcpus, so

s/its'/its/

(That is, drop the spurious apostrophe).


>      b_info->hvm = hvm;
>      b_info->max_vcpus = def->maxvcpus;
> -    b_info->cur_vcpus = def->vcpus;
> +    if (def->vcpus == 32)
> +        b_info->cur_vcpus = 1 << 31;

Still wrong.  You want 32 bits, not one bit:

b_info->cur_vcpus = (uint32_t) -1;

> +    else
> +        b_info->cur_vcpus = (1 << def->vcpus) - 1;
>      if (def->clock.ntimers > 0 &&
>          def->clock.timers[0]->name == VIR_DOMAIN_TIMER_NAME_TSC) {
>          switch (def->clock.timers[0]->mode) {

ACK with those changes.

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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