Re: [Kimchi-devel] [RFC] Allow user to specify max virtual cpus in template and guest

Current State ------------- Currently we have the following values defined for a KVM guest created by Kimchi: <vcpu placement='static' current='4'>252</vcpu> <cpu> <topology sockets='63' cores='2' threads='2'/> </cpu> User specifies the processor topology (optional) and the number of virtual CPUs and sockets are calculated by Kimchi based on maximum supported by the hypervisor (varies with distro) this way: maximum number of virtual cpus supported = 255 (taken from hypervisor) processor topology: cores=2 , threads=2 (optionally specified by user) number of virtual cpus per socket: cores * threads = 4 (from topology) maximum number of sockets guest can have = int(255/4) = 63 maximum number of virtual cpus guest can use = 4 * 63 = 252 Proposal -------- Allow user to specify the maximum number of virtual cpus for a template or guest (when this one is offline - not running). Changes required ---------------- 1) Backend A) Add "maxvcpus" optional field to both template and guest APIs Restrictions to be implemented on this value: - must be a positive integer - must be a multiple of (cores * threads) - must be less than or equal the maximum number of virtual cpus supported by hypervisor If not specified, the default value for maxvcpus will be the equivalent to one socket (that is, core * threads). B) Change the way number of sockets is calculated: maximum number of virtual cpus supported = 255 (taken from hypervisor) topology: cores=2 , threads=2 (specified by user) maximum number of virtual cpus guest can use = 100 (specified by user) number of virtual cpus per socket: cores * threads = 4 (from topology) maximum number of sockets guest can have = int(100/4) = 25 maximum number of virtual cpus guest can use = 4 * 25 = 100 That would result in: <vcpu placement='static' current='4'>100</vcpu> <cpu> <topology sockets='25' cores='2' threads='2'/> </cpu> C) Update/Add unit tests 2) Frontend A) Edit Template, at "Processor" tab: - change the current "CPU number" field to a -[]+ input field (increase/decrease) - add a new -[]+ input field "Max CPU number" (increase/decrease) for user input of "max virtual CPUs". Restrictions from 1.A) apply here. Despite it's in a different place, we may use a "More Options" artifact similar to the one proposed by Rodrigo Trujillo at "[RFC][Kimchi] Guest Max memory setup and update", to keep the same format. B) Edit Guest, at "General" tab: - add a new -[]+ input field "Max CPUs" (increase/decrease in terms of core * threads) for user input of "max virtual CPUs". This new field is only enabled if guest is not running. Restrictions from 1.A) apply here. Let me know your thoughts. Thanks,