From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) (using TLSv1 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 912121A0234 for ; Tue, 17 Jun 2014 18:54:10 +1000 (EST) Message-ID: <53A0022D.5020108@suse.de> Date: Tue, 17 Jun 2014 10:54:05 +0200 From: Alexander Graf MIME-Version: 1.0 To: Madhavan Srinivasan , benh@kernel.crashing.org, paulus@samba.org Subject: Re: [PATCH] powerpc/kvm: support to handle sw breakpoint References: <1402780097-28827-1-git-send-email-maddy@linux.vnet.ibm.com> In-Reply-To: <1402780097-28827-1-git-send-email-maddy@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 14.06.14 23:08, Madhavan Srinivasan wrote: > This patch adds kernel side support for software breakpoint. > Design is that, by using an illegal instruction, we trap to hypervisor > via Emulation Assistance interrupt, where we check for the illegal instruction > and accordingly we return to Host or Guest. Patch mandates use of "abs" instruction > (primary opcode 31 and extended opcode 360) as sw breakpoint instruction. > Based on PowerISA v2.01, ABS instruction has been dropped from the architecture > and treated an illegal instruction. > > Signed-off-by: Madhavan Srinivasan > --- > arch/powerpc/kvm/book3s.c | 3 ++- > arch/powerpc/kvm/book3s_hv.c | 23 +++++++++++++++++++---- > 2 files changed, 21 insertions(+), 5 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c > index c254c27..b40fe5d 100644 > --- a/arch/powerpc/kvm/book3s.c > +++ b/arch/powerpc/kvm/book3s.c > @@ -789,7 +789,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu, > int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu, > struct kvm_guest_debug *dbg) > { > - return -EINVAL; > + vcpu->guest_debug = dbg->control; > + return 0; > } > > void kvmppc_decrementer_func(unsigned long data) > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 7a12edb..688421d 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -67,6 +67,14 @@ > /* Used as a "null" value for timebase values */ > #define TB_NIL (~(u64)0) > > +/* > + * SW_BRK_DBG_INT is debug Instruction for supporting Software Breakpoint. > + * Instruction mnemonic is ABS, primary opcode is 31 and extended opcode is 360. > + * Based on PowerISA v2.01, ABS instruction has been dropped from the architecture > + * and treated an illegal instruction. > + */ > +#define SW_BRK_DBG_INT 0x7c0002d0 The instruction we use to trap needs to get exposed to user space via a ONE_REG property. Also, why don't we use twi always or something else that actually is defined as illegal instruction? I would like to see this shared with book3s_32 PR. > + > static void kvmppc_end_cede(struct kvm_vcpu *vcpu); > static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu); > > @@ -721,12 +729,19 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, > break; > /* > * This occurs if the guest executes an illegal instruction. > - * We just generate a program interrupt to the guest, since > - * we don't emulate any guest instructions at this stage. > + * To support software breakpoint, we check for the sw breakpoint > + * instruction to return back to host, if not we just generate a > + * program interrupt to the guest. > */ > case BOOK3S_INTERRUPT_H_EMUL_ASSIST: > - kvmppc_core_queue_program(vcpu, SRR1_PROGILL); > - r = RESUME_GUEST; > + if (vcpu->arch.last_inst == SW_BRK_DBG_INT) { Don't access last_inst directly. Instead use the provided helpers. > + run->exit_reason = KVM_EXIT_DEBUG; > + run->debug.arch.address = vcpu->arch.pc; > + r = RESUME_HOST; > + } else { > + kvmppc_core_queue_program(vcpu, 0x80000); magic numbers > + r = RESUME_GUEST; > + } > break; > /* > * This occurs if the guest (kernel or userspace), does something that Please enable PR KVM as well while you're at it. Alex