Re: [libvirt PATCH v2 1/2] qemu: remove use of (+|-)name syntax for -cpu featres

On Thu, Oct 07, 2021 at 11:09:19 +0100, Daniel P. Berrangé wrote: > On Thu, Oct 07, 2021 at 11:53:00AM +0200, Jiri Denemark wrote: > > On Thu, Oct 07, 2021 at 10:05:12 +0100, Daniel P. Berrangé wrote: > > > The -cpu arg gained support for feature=on|off syntax for the x86 > > > emulator in 2.4.0 > > > > > > commit 38e5c119c2925812bd441450ab9e5e00fc79e662 > > > Author: Eduardo Habkost <ehabkost(a)redhat.com&gt; > > > Date: Mon Mar 23 17:29:32 2015 -0300 > > > > > > target-i386: Register QOM properties for feature flags > > > > > > Most other targets gained this syntax even earlier in 1.4.1 > > > > > > commit 1590bbcb02921dfe8e3cf66e3a3aafd31193babf > > > Author: Andreas Färber <afaerber(a)suse.de&gt; > > > Date: Mon Mar 3 23:33:51 2014 +0100 > > > > > > cpu: Implement CPUClass::parse_features() for the rest of CPUs > > > > > > CPUs who do not provide their own implementation of feature parsing > > > will treat each option as a QOM property and set it to the supplied > > > value. > > > > > > There appears no reason to keep supporting "+|-feature" syntax, > > > given the current minimum QEMU version. > > > > > > Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; > > > --- > > > src/qemu/qemu_command.c | 34 ++++++------------- > > > tests/qemuxml2argvdata/cpu-Haswell2.args | 2 +- > > > tests/qemuxml2argvdata/cpu-Haswell3.args | 2 +- > > > .../qemuxml2argvdata/cpu-cache-disable3.args | 2 +- > > > .../cpu-check-default-partial.args | 2 +- > > > tests/qemuxml2argvdata/cpu-eoi-disabled.args | 2 +- > > > tests/qemuxml2argvdata/cpu-eoi-enabled.args | 2 +- > > > tests/qemuxml2argvdata/cpu-exact1.args | 2 +- > > > .../cpu-exact2-nofallback.args | 2 +- > > > tests/qemuxml2argvdata/cpu-exact2.args | 2 +- > > > tests/qemuxml2argvdata/cpu-fallback.args | 2 +- > > > tests/qemuxml2argvdata/cpu-host-kvmclock.args | 2 +- > > > .../qemuxml2argvdata/cpu-host-model-cmt.args | 2 +- > > > .../cpu-host-model-fallback.args | 2 +- > > > .../cpu-host-model-vendor.args | 2 +- > > > tests/qemuxml2argvdata/cpu-host-model.args | 2 +- > > > .../cpu-host-passthrough-features.args | 2 +- > > > tests/qemuxml2argvdata/cpu-kvmclock.args | 2 +- > > > tests/qemuxml2argvdata/cpu-minimum1.args | 2 +- > > > tests/qemuxml2argvdata/cpu-minimum2.args | 2 +- > > > tests/qemuxml2argvdata/cpu-strict1.args | 2 +- > > > .../cpu-translation.x86_64-latest.args | 2 +- > > > tests/qemuxml2argvdata/cpu-tsc-frequency.args | 2 +- > > > .../eoi-disabled.x86_64-latest.args | 2 +- > > > .../eoi-enabled.x86_64-latest.args | 2 +- > > > .../graphics-spice-timeout.args | 2 +- > > > .../kvmclock+eoi-disabled.x86_64-latest.args | 2 +- > > > tests/qemuxml2argvdata/kvmclock.args | 2 +- > > > .../pci-bridge-many-disks.args | 2 +- > > > .../pv-spinlock-disabled.x86_64-latest.args | 2 +- > > > .../pv-spinlock-enabled.x86_64-latest.args | 2 +- > > > 31 files changed, 41 insertions(+), 53 deletions(-) > > > > > > diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c > > > index eaa1e0deb9..0f1cdd9372 100644 > > > --- a/src/qemu/qemu_command.c > > > +++ b/src/qemu/qemu_command.c > > > @@ -6242,21 +6242,6 @@ qemuBuildGlobalControllerCommandLine(virCommand *cmd, > > > } > > > > > > > > > -static void > > > -qemuBuildCpuFeature(virQEMUCaps *qemuCaps, > > > - virBuffer *buf, > > > - const char *name, > > > - bool state) > > > -{ > > > - name = virQEMUCapsCPUFeatureToQEMU(qemuCaps, name); > > > - > > > - if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_QUERY_CPU_MODEL_EXPANSION)) > > > - virBufferAsprintf(buf, ",%s=%s", name, state ? "on" : "off"); > > > - else > > > - virBufferAsprintf(buf, ",%c%s", state ? '+' : '-', name); > > > -} > > > > I guess it would have been easier and perhaps clearer to just remove the > > else branch and the test itself, because... > > > > > @@ -6433,13 +6420,14 @@ qemuBuildCpuCommandLine(virCommand *cmd, > > > } > > > > > > if (def->apic_eoi) { > > > - qemuBuildCpuFeature(qemuCaps, &buf, "kvm_pv_eoi", > > > - def->apic_eoi == VIR_TRISTATE_SWITCH_ON); > > > + virBufferAsprintf(&buf, ",kvm_pv_eoi=%s", def->apic_eoi == > > > + VIR_TRISTATE_SWITCH_ON ? "on" : "off"); > > > > This is affected by the same issue spotted by Peter in v1. In other > > words, when replacing qemuBuildCpuFeature you need to make sure the > > feature name goes through virQEMUCapsCPUFeatureToQEMU(). > > virQEMUCapsCPUFeatureToQEMU() is a constant mapping. It makes sense > to use it in the earlier loop, because we're getting feature names > dynamically from the XML config. > > In this case though, we've just got a constant string. Seems better > to just pass the right constant string in directly rather than send > it through this remapping. Well, only when QEMU_CAPS_CANONICAL_CPU_FEATURES is set. If it is always set for any QEMU we deal with, we can just drop it too, though.