From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabiano Rosas Date: Mon, 17 Jun 2019 19:25:49 +0000 Subject: Re: [PATCH v2] KVM: PPC: Report single stepping capability Message-Id: <87y3202ev6.fsf@linux.ibm.com> List-Id: References: <20190529222219.27994-1-farosas@linux.ibm.com> <20190617061608.y5qw26i53si76qqt@oak.ozlabs.ibm.com> In-Reply-To: <20190617061608.y5qw26i53si76qqt@oak.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Paul Mackerras Cc: kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, benh@kernel.crashing.org, mpe@ellerman.id.au, pbonzini@redhat.com, rkrcmar@redhat.com, david@gibson.dropbear.id.au, aik@ozlabs.ru Paul Mackerras writes: > On Wed, May 29, 2019 at 07:22:19PM -0300, Fabiano Rosas wrote: >> When calling the KVM_SET_GUEST_DEBUG ioctl, userspace might request >> the next instruction to be single stepped via the >> KVM_GUESTDBG_SINGLESTEP control bit of the kvm_guest_debug structure. >> >> We currently don't have support for guest single stepping implemented >> in Book3S HV. >> >> This patch adds the KVM_CAP_PPC_GUEST_DEBUG_SSTEP capability in order >> to inform userspace about the state of single stepping support. > > Comment/question below: > >> --- a/arch/powerpc/kvm/powerpc.c >> +++ b/arch/powerpc/kvm/powerpc.c >> @@ -538,6 +538,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> case KVM_CAP_IMMEDIATE_EXIT: >> r = 1; >> break; >> + case KVM_CAP_PPC_GUEST_DEBUG_SSTEP: >> +#ifdef CONFIG_BOOKE >> + r = 1; >> + break; >> +#endif > > In the !CONFIG_BOOKE case, this will fall through to code which will > return 0 for HV KVM or 1 for PR KVM. Is that what was intended? Yes. The intention is to return 0 for HV and 1 for everything else. > If so, then why do we need the CONFIG_BOOKE case? Isn't hv_enabled > always 0 on Book E? Good point. I made a mistake there indeed. > In any case, I think this needs at least a /* fall through */ comment > in the code, and something explicit in the patch description to say > that we intend to return 1 on PR KVM. I'll send another version. Thanks