Re: SIGSEGV with -smp 17+, and error handling around...

[Avi Kivity <avi@redhat.com>]

On 03/17/2010 10:12 PM, Michael Tokarev wrote:
> When run with -smp 17 or greather, kvm
> fails like this:
>
> $ kvm -smp 17
> kvm_create_vcpu: Invalid argument
> kvm_setup_mce FAILED: Invalid argument
> KVM_SET_LAPIC failed
> Segmentation fault
> $ _
>
> In qemu-kvm.c, the kvm_create_vcpu() routine
> (which is used in a vcpu thread to set up
> vcpu) is declared as void, i.e, no error
> return.  And the code that calls it blindly
> assumes that it will never fail...
>
> But the first error message above is from kernel,
> which - apparently - refuses to create 17th vCPU.
> Hence we've a vcpu thread which is empty/dummy and
> not even fully initialized... so it fails later
> in the game.
>
> This all looks quite... raw, not polished ;)
>
> Can we somehow handle the (several possible) errors
> in that (and other) places, and how we ever can act
> on them?  Abort?  Warn the user and reduce the number
> of vcpus accordingly (seems wrong, esp. if it were
> some first vcpus or in the middle which failed)...
>    

A patch from Alex fixing this was just committed.  I'll apply it to the 
stable branch as well.

-- 
error compiling committee.c: too many arguments to function