Re: [libvirt] [PATCH 1/2] qemu: do not define known no-op features

Qemu dropped cpu features for osxsave and ospke [1][2]. The reason for the instant removal is that those features were never configurable as discussed in [3]. Fortunately the use cases adding those flags in the past are rare, but they exist. One that I identified are e.g. older virt-install when used with --cpu=host-model and there always could be the case of a user adding it to the guest xml. This triggers an issue like: qemu-system-x86_64: can't apply global Broadwell-noTSX-x86_64- cpu.osxsave=on: Property '.osxsave' not found Ensure that this does no more break spawning newer qemu versions by not rendering those features into the qemu command line. Fixes: https://bugs.launchpad.net/fedora/+source/qemu/+bug/1825195 Resolves: https://bugzilla.redhat.com/1644848

[1]: https://git.qemu.org/?p=qemu.git;a=commit;h=f1a2352 [2]: https://git.qemu.org/?p=qemu.git;a=commit;h=9ccb978 [3]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg561877.html Signed-off-by: Christian Ehrhardt <christian.ehrhardt(a)canonical.com&gt; --- src/qemu/qemu_command.c | 23 +++++++++++++++++++ .../qemuxml2argvdata/cpu-host-model-cmt.args | 2 +- tests/qemuxml2argvdata/cpu-tsc-frequency.args | 4 ++-- 3 files changed, 26 insertions(+), 3 deletions(-) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 1425d97b1e..e0c8ae50a1 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7076,6 +7076,27 @@ qemuBuildGlobalControllerCommandLine(virCommandPtr cmd, return 0; } +/** + * qemuFeatureNoEffect: + * @feature: CPU Feature + * + * Returns true, if the feature is known to have (never had) an effect on QEMU. + * Those features might be dropped in qemu without a longer deprecation cycle + * and must therefore be known e.g. to no more define them on command line. + */ +static bool +qemuFeatureNoEffect(virCPUFeatureDefPtr feature) +{ + if (!feature->name) + return false; + + if (STREQ(feature->name, "osxsave")) + return true; + if (STREQ(feature->name, "ospke")) + return true; + + return false; +} static int qemuBuildCpuModelArgStr(virQEMUDriverPtr driver, @@ -7144,6 +7165,8 @@ qemuBuildCpuModelArgStr(virQEMUDriverPtr driver, virBufferAsprintf(buf, ",vendor=%s", cpu->vendor_id); for (i = 0; i < cpu->nfeatures; i++) { + if (qemuFeatureNoEffect(&(cpu->features[i]))) + continue; switch ((virCPUFeaturePolicy) cpu->features[i].policy) { case VIR_CPU_FEATURE_FORCE: case VIR_CPU_FEATURE_REQUIRE: diff --git a/tests/qemuxml2argvdata/cpu-host-model-cmt.args b/tests/qemuxml2argvdata/cpu-host-model-cmt.args index 36f706b836..42f969fd62 100644 --- a/tests/qemuxml2argvdata/cpu-host-model-cmt.args +++ b/tests/qemuxml2argvdata/cpu-host-model-cmt.args @@ -12,7 +12,7 @@ QEMU_AUDIO_DRV=none \ -S \ -machine pc,accel=tcg,usb=off,dump-guest-core=off \ -cpu Haswell,+vme,+ds,+acpi,+ss,+ht,+tm,+pbe,+dtes64,+monitor,+ds_cpl,+vmx,\ -+smx,+est,+tm2,+xtpr,+pdcm,+osxsave,+f16c,+rdrand,+pdpe1gb,+abm,+lahf_lm \ ++smx,+est,+tm2,+xtpr,+pdcm,+f16c,+rdrand,+pdpe1gb,+abm,+lahf_lm \ -m 214 \ -realtime mlock=off \ -smp 6,sockets=6,cores=1,threads=1 \ diff --git a/tests/qemuxml2argvdata/cpu-tsc-frequency.args b/tests/qemuxml2argvdata/cpu-tsc-frequency.args index 55bcf89617..55b72b4404 100644 --- a/tests/qemuxml2argvdata/cpu-tsc-frequency.args +++ b/tests/qemuxml2argvdata/cpu-tsc-frequency.args @@ -12,8 +12,8 @@ QEMU_AUDIO_DRV=none \ -S \ -machine pc,accel=kvm,usb=off,dump-guest-core=off \ -cpu Haswell,+vme,+ds,+acpi,+ss,+ht,+tm,+pbe,+dtes64,+monitor,+ds_cpl,+vmx,\ -+smx,+est,+tm2,+xtpr,+pdcm,+osxsave,+f16c,+rdrand,+pdpe1gb,+abm,+lahf_lm,\ -+invtsc,tsc-frequency=3504000000 \ ++smx,+est,+tm2,+xtpr,+pdcm,+f16c,+rdrand,+pdpe1gb,+abm,+lahf_lm,+invtsc,\ +tsc-frequency=3504000000 \ -m 214 \ -realtime mlock=off \ -smp 1,sockets=1,cores=1,threads=1 \