Re: [PATCH 13/50] KVM: PPC: booke: check for signals in kvmppc_vcpu_run

[Avi Kivity <avi@redhat.com>]

On 01/08/2012 05:11 PM, Alexander Graf wrote:
> On 08.01.2012, at 14:18, Avi Kivity wrote:
>
> > On 01/04/2012 03:10 AM, Alexander Graf wrote:
> >> From: Scott Wood <scottwood@freescale.com>
> >> 
> >> Currently we check prior to returning from a lightweight exit,
> >> but not prior to initial entry.
> >> 
> >> book3s already does a similar test.
> >> 
> >> Signed-off-by: Scott Wood <scottwood@freescale.com>
> >> Signed-off-by: Alexander Graf <agraf@suse.de>
> >> ---
> >> arch/powerpc/kvm/booke.c |   10 +++++++++-
> >> 1 files changed, 9 insertions(+), 1 deletions(-)
> >> 
> >> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> >> index b642200..9c78589 100644
> >> --- a/arch/powerpc/kvm/booke.c
> >> +++ b/arch/powerpc/kvm/booke.c
> >> @@ -322,11 +322,19 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> >> 	}
> >> 
> >> 	local_irq_disable();
> >> +
> >> +	if (signal_pending(current)) {
> >> +		kvm_run->exit_reason = KVM_EXIT_INTR;
> >> +		ret = -EINTR;
> >> +		goto out;
> >> +	}
> >> +
> >> 	kvm_guest_enter();
> >> 	ret = __kvmppc_vcpu_run(kvm_run, vcpu);
> >> 	kvm_guest_exit();
> >> -	local_irq_enable();
> >> 
> >> 
> > 
> > In general a single check prior to entry is sufficient (well, in
> > addition to the one in kvm_vcpu_block()).
>
> Yes, and IIUC this is the single check prior to entry. On lightweight exit, we don't return from __kvmppc_vcpu_run, but only call kvmppc_handle_exit() and if that exits that we return to the guest, we stay inside of __kvmppc_vcpu_run and don't return from here.

It means you check twice per heavyweight exit, no?  Once here, and once
when kvmppc_handle_exit() returns.  If, instead, you move the check to
just before the lightweight entry, you check just once per entry, like x86.

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