Re: Can we force a KVM VCPU in Guest Mode to Exit to User Mode From User Mode ?

[Avi Kivity <avi@redhat.com>]

On 07/26/2012 12:38 PM, Mian M. Hamayun wrote:

<snip>

> 
> This mechanism 'seems' to work fine when both vcpu threads are in User
> Mode. But when booting an SMP Guest, the boot processor (BSP) initially
> executes the bootstrap code while the non-boot processors (APs) are
> waiting for initial INIT-SIPI-SIPI messages.
> 
> What I fail to understand is if an AP is currently waiting for an INIT
> signal, and we call the "run_on_cpu" function above for this cpu, it
> blocks the whole system, as the AP is in Guest mode and cannot call the
> "flush_queued_work" and the BSP is waiting for this to happen.
> 
> How can we resolve this deadlock ? Is there a way to force the AP to
> quit the Guest Mode, by using some specific mechanism from the User mode ?

When a vcpu is waiting for an INIT, it still responds to signals and
will return to userspace if a signal is received.  Did you observe
something different?


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error compiling committee.c: too many arguments to function