[8/8] KVM:PPC:booke: Allow debug interrupt injection to guest

> -----Original Message-----
> From: kvm-owner@vger.kernel.org [mailto:kvm-owner@vger.kernel.org] On Behalf Of
> Alexander Graf
> Sent: Thursday, January 31, 2013 5:34 PM
> To: Bhushan Bharat-R65777
> Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org
> Subject: Re: [PATCH 8/8] KVM:PPC:booke: Allow debug interrupt injection to guest
> 
> 
> On 30.01.2013, at 12:12, Bhushan Bharat-R65777 wrote:
> 
> >
> >
> >> -----Original Message-----
> >> From: kvm-ppc-owner@vger.kernel.org
> >> [mailto:kvm-ppc-owner@vger.kernel.org] On Behalf Of Alexander Graf
> >> Sent: Friday, January 25, 2013 5:44 PM
> >> To: Bhushan Bharat-R65777
> >> Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; Bhushan
> >> Bharat-R65777
> >> Subject: Re: [PATCH 8/8] KVM:PPC:booke: Allow debug interrupt
> >> injection to guest
> >>
> >>
> >> On 16.01.2013, at 09:24, Bharat Bhushan wrote:
> >>
> >>> Allow userspace to inject debug interrupt to guest. QEMU can
> >>
> >> s/QEMU/user space.
> >>
> >>> inject the debug interrupt to guest if it is not able to handle the
> >>> debug interrupt.
> >>>
> >>> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> >>> ---
> >>> arch/powerpc/kvm/booke.c  |   32 +++++++++++++++++++++++++++++++-
> >>> arch/powerpc/kvm/e500mc.c |   10 +++++++++-
> >>> 2 files changed, 40 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> >>> index faa0a0b..547797f 100644
> >>> --- a/arch/powerpc/kvm/booke.c
> >>> +++ b/arch/powerpc/kvm/booke.c
> >>> @@ -133,6 +133,13 @@ static void kvmppc_vcpu_sync_fpu(struct
> >>> kvm_vcpu
> >>> *vcpu) #endif }
> >>>
> >>> +#ifdef CONFIG_KVM_BOOKE_HV
> >>> +static int kvmppc_core_pending_debug(struct kvm_vcpu *vcpu) {
> >>> +	return test_bit(BOOKE_IRQPRIO_DEBUG,
> >>> +&vcpu->arch.pending_exceptions); } #endif
> >>> +
> >>> /*
> >>> * Helper function for "full" MSR writes.  No need to call this if
> >>> only
> >>> * EE/CE/ME/DE/RI are changing.
> >>> @@ -144,7 +151,11 @@ void kvmppc_set_msr(struct kvm_vcpu *vcpu, u32
> >>> new_msr) #ifdef CONFIG_KVM_BOOKE_HV
> >>> 	new_msr |= MSR_GS;
> >>>
> >>> -	if (vcpu->guest_debug)
> >>> +	/*
> >>> +	 * Set MSR_DE if the hardware debug resources are owned by user-space
> >>> +	 * and there is no debug interrupt pending for guest to handle.
> >>
> >> Why?
> >
> > QEMU is using the IAC/DAC registers to set hardware breakpoint/watchpoints via
> debug ioctls. As debug events are enabled/gated by MSR_DE so somehow we need to
> set MSR_DE on hardware MSR when guest is running in this case.
> 
> Reading this 5 times I still have no idea what you're really checking for here.
> Maybe the naming for kvmppc_core_pending_debug is just unnatural? What does that
> function do really?
> 
> >
> > On bookehv this is how I am controlling the MSR_DE in hardware MSR.
> >
> >> And why is this whole thing only executed on HV?
> >
> > On e500v2 we always enable MSR_DE using vcpu->arch.shadow_msr in
> > e500.c #ifndef CONFIG_KVM_BOOKE_HV
> > -       vcpu->arch.shadow_msr = MSR_USER | MSR_IS | MSR_DS;
> > +       vcpu->arch.shadow_msr = MSR_USER | MSR_DE | MSR_IS | MSR_DS;


> Why? How is e500v2 any different wrt debug? And why wouldn't that work for
> e500mc?
> 
> 
> Alex
> 
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