On Sun, Sep 19, 2010 at 04:07:50PM +0200, Conrad Wood wrote: > On Sun, 2010-09-19 at 15:50 +0200, Gleb Natapov wrote: > > On Sun, Sep 19, 2010 at 09:46:21AM -0400, Kevin O'Connor wrote: > > > On Sun, Sep 19, 2010 at 03:40:45PM +0200, Gleb Natapov wrote: > > > > halted state is not the way to check for whether cpu is online or > > > > offline. cpu may be online but executing hlt instruction so > > > > its state will be halted, but cpu itself is online. Actually with kvm > > > > today you are not able to check that cpu is offline if it was ever > > > > online. Query a guest for cpu status. > > > > > > In that regard, "info cpus" does seem to work - as it only shows me > > > the cpus that have ever been online. Ejecting a cpu in the guest does > > > not remove it from "info cpus", but then, I don't think kvm does > > > remove it from being available after an eject. > > > > > Exactly. That what I meant by "Actually with kvm today you are not able > > to check that cpu is offline if it was ever online". So if cpu was never > > online it is easy to check that it is offline (it will not be reported > > by "info cpus"). But if it was inserted and then ejected it will still > > be present in "info cpus", but not used by a guest OS. > > > > -- > > Gleb. > > > > 1) Thanks for clarifying "online" vs "halted" - that makes sense and is > probably part of what confused me. I need to get the "online/offline" > status of cpus, not if they are halted or not. I understand this is > currently not possible with kvm. As I have no direct control over the > guest OS, I do however need a solution on the host. Any clues how this > could be implemented would be much appreciated. > This is important to me. Lets establish some terminology to understand each other better: Lets use CPU inserted/ejected to refer to cpu being available/not available to a guest. Lest use CPU online/offline to refer to cpu been used by a guest OS. CPU hot-plug works like this: cpu is inserted (plugged into cpu socket on MB) guest OS is notifies through ACPI guest OS starts to use newly added CPU (makes it online) CPU hot-unplug works like this: guest OS is notifies through ACPI that cpu is going to be removed guest OS stops to use cpu (makes it offline) cpu is ejected (removed from a socket on MB) (kvm never does that part) So which part do you want to know about from a host? You can't really know from a host if cpu is used by guest OS (if it is online/offline in s guest in our terminology) inserted/ejected is management action (it can't be initiated by a guest), so you can keep track of it by yourself. KVM doesn't do it for you right now. More precisely it does, but doesn't have a way to quire it. > > 2) In my case, the cpus are ALWAYS reported as halted, regardless of the > current state in the guest. This is cosmetic but. It does not affect any operation. > After the guest booted, The "cpu infos" displays precisely the amount of > cpus as initially set by the -smp parameter of kvm. (as halted). > any additional cpus added later will be displayed, also as halted - > again regardless whether or not the guest switches or had switched them > to online. It is reported as "halted" even whilst the guest is running a > cpu-hogger which would stop the cpu from halting. > I don't mind so much about this cosmetic display problem ;) > Rightly so since even when it works information it displays is already outdated at the moment you see it anyway. It is useful for debugging, thus I keep fixing it when it breaks. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
