> -----Original Message----- > From: Alexander Graf [mailto:agraf@xxxxxxx] > Sent: Monday, July 28, 2014 7:35 PM > To: Bhushan Bharat-R65777; kvm-ppc@xxxxxxxxxxxxxxx > Cc: kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421; Yoder Stuart-B08248 > Subject: Re: [PATCH 6/6] KVM: PPC: BOOKE: Emulate debug registers and exception > > > On 11.07.14 10:39, Bharat Bhushan wrote: > > This patch emulates debug registers and debug exception to support > > guest using debug resource. This enables running gdb/kgdb etc in > > guest. > > > > On BOOKE architecture we cannot share debug resources between QEMU and > > guest because: > > When QEMU is using debug resources then debug exception must > > be always enabled. To achieve this we set MSR_DE and also set > > MSRP_DEP so guest cannot change MSR_DE. > > > > When emulating debug resource for guest we want guest > > to control MSR_DE (enable/disable debug interrupt on need). > > > > So above mentioned two configuration cannot be supported > > at the same time. So the result is that we cannot share > > debug resources between QEMU and Guest on BOOKE architecture. > > > > In the current design QEMU gets priority over guest, this means that > > if QEMU is using debug resources then guest cannot use them and if > > guest is using debug resource then QEMU can overwrite them. > > > > Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx> > > --- > > Hi Alex, > > > > I thought of having some print in register emulation if QEMU is using > > debug resource, Also when QEMU overwrites guest written values but > > that looks excessive. If I uses some variable which get set when guest > > starts using debug registers and check in debug set ioctl then that > > look ugly. Looking for suggestions > > Whatever you do, have QEMU do the print, not the kernel. > > > > > arch/powerpc/include/asm/kvm_ppc.h | 3 + > > arch/powerpc/kvm/booke.c | 27 +++++++ > > arch/powerpc/kvm/booke_emulate.c | 157 > +++++++++++++++++++++++++++++++++++++ > > 3 files changed, 187 insertions(+) > > > > diff --git a/arch/powerpc/include/asm/kvm_ppc.h > > b/arch/powerpc/include/asm/kvm_ppc.h > > index e2fd5a1..f3f7611 100644 > > --- a/arch/powerpc/include/asm/kvm_ppc.h > > +++ b/arch/powerpc/include/asm/kvm_ppc.h > > @@ -173,6 +173,9 @@ extern int kvmppc_xics_get_xive(struct kvm *kvm, u32 irq, > u32 *server, > > extern int kvmppc_xics_int_on(struct kvm *kvm, u32 irq); > > extern int kvmppc_xics_int_off(struct kvm *kvm, u32 irq); > > > > +void kvmppc_core_dequeue_debug(struct kvm_vcpu *vcpu); void > > +kvmppc_core_queue_debug(struct kvm_vcpu *vcpu); > > + > > union kvmppc_one_reg { > > u32 wval; > > u64 dval; > > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index > > fadfe76..c2471ed 100644 > > --- a/arch/powerpc/kvm/booke.c > > +++ b/arch/powerpc/kvm/booke.c > > @@ -264,6 +264,16 @@ static void kvmppc_core_dequeue_watchdog(struct kvm_vcpu > *vcpu) > > clear_bit(BOOKE_IRQPRIO_WATCHDOG, &vcpu->arch.pending_exceptions); > > } > > > > +void kvmppc_core_queue_debug(struct kvm_vcpu *vcpu) { > > + kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_DEBUG); } > > + > > +void kvmppc_core_dequeue_debug(struct kvm_vcpu *vcpu) { > > + clear_bit(BOOKE_IRQPRIO_DEBUG, &vcpu->arch.pending_exceptions); } > > + > > static void set_guest_srr(struct kvm_vcpu *vcpu, unsigned long srr0, u32 > srr1) > > { > > #ifdef CONFIG_KVM_BOOKE_HV > > @@ -783,6 +793,23 @@ static int kvmppc_handle_debug(struct kvm_run *run, > struct kvm_vcpu *vcpu) > > struct debug_reg *dbg_reg = &(vcpu->arch.shadow_dbg_reg); > > u32 dbsr = vcpu->arch.dbsr; > > > > + if (vcpu->guest_debug == 0) { > > + /* Debug resources belong to Guest */ > > + if (dbsr && (vcpu->arch.shared->msr & MSR_DE)) > > + kvmppc_core_queue_debug(vcpu); > > + > > + /* Inject a program interrupt if trap debug is not allowed */ > > + if ((dbsr & DBSR_TIE) && !(vcpu->arch.shared->msr & MSR_DE)) > > + kvmppc_core_queue_program(vcpu, ESR_PTR); > > In that case we would've received a program interrupt and never entered this > code path, no? Yes for HV. But for PR we can be here, MSR_DE is set in h/w msr and guest MSR_DE is not set. Having a ifdef does not look good but we can have a comment here. Thanks -Bharat > > > Alex -- 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
