On Thu, Apr 14, 2016 at 10:55:07PM +0200, Radim Krčmář wrote: > QEMU complains about -cpu host on an AMD machine: > warning: host doesn't support requested feature: CPUID.80000001H:EDX [bit 0] > For bits 0,1,3,4,5,6,7,8,9,12,13,14,15,16,17,23,24. > > Host does support them, but x86_cpu_get_migratable_flags filters unnamed > features and drops these bits without realizing that they are aliases to > CPUID.1H:EDX and have their names there. > > See https://bugzilla.redhat.com/show_bug.cgi?id=1326721 for details. > > Signed-off-by: Radim Krčmář <rkrc...@redhat.com> > --- > target-i386/cpu.c | 40 ++++++++++++++++++++++------------------ > 1 file changed, 22 insertions(+), 18 deletions(-) > > diff --git a/target-i386/cpu.c b/target-i386/cpu.c > index ddae932ee1b4..66bd9d0c4039 100644 > --- a/target-i386/cpu.c > +++ b/target-i386/cpu.c > @@ -506,7 +506,7 @@ const char *get_register_name_32(unsigned int reg) > * Returns the set of feature flags that are supported and migratable by > * QEMU, for a given FeatureWord. > */ > -static uint32_t x86_cpu_get_migratable_flags(FeatureWord w) > +static uint32_t x86_cpu_get_migratable_flags(FeatureWord w, bool is_amd) > { > FeatureWordInfo *wi = &feature_word_info[w]; > uint32_t r = 0; > @@ -514,12 +514,18 @@ static uint32_t > x86_cpu_get_migratable_flags(FeatureWord w) > > for (i = 0; i < 32; i++) { > uint32_t f = 1U << i; > + FeatureWordInfo *effective_wi = wi; > + > + if (is_amd && w == FEAT_8000_0001_EDX && f & CPUID_EXT2_AMD_ALIASES) > { > + effective_wi = &feature_word_info[FEAT_1_EDX]; > + } > + > /* If the feature name is unknown, it is not supported by QEMU yet */ > - if (!wi->feat_names[i]) { > + if (!effective_wi->feat_names[i]) { > continue; > } > /* Skip features known to QEMU, but explicitly marked as > unmigratable */ > - if (wi->unmigratable_flags & f) { > + if (effective_wi->unmigratable_flags & f) { > continue; > } > r |= f;
I don't think we need that complexity to fix the problem. We even have a similar hack in kvm_arch_get_supported_cpuid() to make sure it handles the alias bits properly. Instead of hacking those functions to copy CPUID[1] data, it's much easier to simply copy the alias bits in realizefn after we call x86_cpu_filter_features(), not before. The following (untested) fix should be sufficient: diff --git a/target-i386/cpu.c b/target-i386/cpu.c index ddae932..d0b5b69 100644 --- a/target-i386/cpu.c +++ b/target-i386/cpu.c @@ -2897,6 +2897,14 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp) env->cpuid_level = 7; } + if (x86_cpu_filter_features(cpu) && cpu->enforce_cpuid) { + error_setg(&local_err, + kvm_enabled() ? + "Host doesn't support requested features" : + "TCG doesn't support requested features"); + goto out; + } + /* On AMD CPUs, some CPUID[8000_0001].EDX bits must match the bits on * CPUID[1].EDX. */ @@ -2907,14 +2915,6 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp) } - if (x86_cpu_filter_features(cpu) && cpu->enforce_cpuid) { - error_setg(&local_err, - kvm_enabled() ? - "Host doesn't support requested features" : - "TCG doesn't support requested features"); - goto out; - } - #ifndef CONFIG_USER_ONLY qemu_register_reset(x86_cpu_machine_reset_cb, cpu); -- Eduardo