On Wed, 25 Jul 2018 13:58:16 +0200 David Hildenbrand <da...@redhat.com> wrote:
> On 25.07.2018 13:36, Cornelia Huck wrote: > > On Wed, 25 Jul 2018 11:12:33 +0200 > > David Hildenbrand <da...@redhat.com> wrote: > > > >> The "max" CPU model behaves like "-cpu host" when KVM is enabled, and like > >> a CPU with the maximum possible feature set when TCG is enabled. > >> > >> While the "host" model can not be used under TCG ("kvm_required"), the > >> "max" model can and "Enables all features supported by the accelerator in > >> the current host". > >> > >> So we can treat "host" just as a special case of "max" (like x86 does). > >> It differs to the "qemu" CPU model under TCG such that compatibility > >> handling will not be performed and that some experimental CPU features > >> not yet part of the "qemu" model might be indicated. > >> > >> These are right now under TCG (see "qemu_MAX"): > >> - stfle53 > > > > That's a z13 feature, so I think it's fine as we don't care about > > machine generations for the max mode anyway, correct? > > Yes the max model really just is "give me anything you got and that you > can expand to a static model (i.e. fully specify on the command line)". > > > > >> - msa5-base > > > > That's just the warning, but as things are continuing to work, it's > > fine as well. > > Yes, as these are z13 models we don't but them yet into our "stable" > qemu model which is based on a z12. > > > > >> - zpci > > > > That one theoretically has a dependency on CONFIG_PCI, but as that is > > always set, I think it's fine as well. > > That is even already handled correctly, see > target/s390x/cpu_models.c:register_types() > > 1314 #ifndef CONFIG_USER_ONLY > 1315 if (!pci_available) { > 1316 clear_bit(S390_FEAT_ZPCI, qemu_max_cpu_feat); > 1317 } > 1318 #endif Oh, I actually added that myself :) > > [...] > > > Maybe add a comment that for kvm we try the host model, and only that > > can fail (i.e., for tcg this will always work)? > > "we expect only errors under KVM, when we actually query the kernel" "We expect errors only under KVM, where we actually query the kernel" ? If nobody else has further comments, I can squash in the change and queue it for 3.1. I'll let it sit for a bit longer on the list, though. > > > > >> + error_report_err(local_err); > >> + /* fallback to unsupported CPU models */ > >> + return; > >> + } > >> + > >> + cpu->model = g_new(S390CPUModel, 1); > >> + /* copy the CPU model so we can modify it */ > >> + memcpy(cpu->model, max_model, sizeof(*cpu->model)); > >> +} > >> + > >> static void s390_cpu_model_finalize(Object *obj) > >> { > >> S390CPU *cpu = S390_CPU(obj); > > > > Looks sane to me. > > > > Thanks! >