From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabiano Rosas Date: Thu, 21 Mar 2019 14:35:54 +0000 Subject: Re: [RFC PATCH 1/1] KVM: PPC: Report single stepping capability Message-Id: <87va0ce1md.fsf@linux.ibm.com> List-Id: References: <20190320183951.29537-1-farosas@linux.ibm.com> <20190320183951.29537-2-farosas@linux.ibm.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alexey Kardashevskiy , kvm-ppc@vger.kernel.org Cc: kvm@vger.kernel.org, rkrcmar@redhat.com, pbonzini@redhat.com, linuxppc-dev@lists.ozlabs.org, david@gibson.dropbear.id.au Alexey Kardashevskiy writes: > In the cover letter (which is not really required for a single patch) > you say the capability will be present for BookE and PR KVM (which > Book3s) but here it is BookE only, is that intentional? A few lines below (falling through) we have: /* We support this only for PR */ r = !hv_enabled; > Also, you need to update Documentation/virtual/kvm/api.txt for the new > capability. After reading which I started wondering could not we just > use existing KVM_CAP_GUEST_DEBUG_HW_BPS? We _could_, but I think that would conflate two different concepts. Single stepping does not necessarily makes use of hardware breakpoints (e.g. Trace Interrupt on Book3s PR). I also think we should use KVM_CAP_GUEST_DEBUG_HW_BPS in the future to let QEMU know about: i) the lack of hardware breakpoints in Book3s and ii) BookE's hardware breakpoints (Instruction Address Compare) that are currently not being reported via HW_BPS.