| Message ID | 20200904145431.196885-13-vkuznets@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | i386: KVM: expand Hyper-V features early | expand |
On Fri, Sep 04, 2020 at 04:54:21PM +0200, Vitaly Kuznetsov wrote: > We have all the required data in X86CPU already and as we are about to > split hyperv_handle_properties() into hyperv_expand_features()/ > hyperv_fill_cpuids() we can remove the blind copy. The functional change > is that QEMU won't pass CPUID leaves it doesn't currently know about > to the guest but arguably this is a good change. Is it, though? Maybe we don't want it to be the default, but a blind passthrough mode that copies all CPUID leaves would be useful for testing new features. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > target/i386/kvm.c | 9 --------- > 1 file changed, 9 deletions(-) > > diff --git a/target/i386/kvm.c b/target/i386/kvm.c > index 87b83a2aa2cb..b7f0e200a75f 100644 > --- a/target/i386/kvm.c > +++ b/target/i386/kvm.c > @@ -1221,9 +1221,6 @@ static int hyperv_handle_properties(CPUState *cs, > } > > if (cpu->hyperv_passthrough) { > - memcpy(cpuid_ent, &cpuid->entries[0], > - cpuid->nent * sizeof(cpuid->entries[0])); > - > c = cpuid_find_entry(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 0); > if (c) { > cpu->hyperv_vendor_id[0] = c->ebx; > @@ -1325,12 +1322,6 @@ static int hyperv_handle_properties(CPUState *cs, > goto free; > } > > - if (cpu->hyperv_passthrough) { > - /* We already copied all feature words from KVM as is */ > - r = cpuid->nent; > - goto free; > - } > - > c = &cpuid_ent[cpuid_i++]; > c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS; > c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ? > -- > 2.25.4 >
Eduardo Habkost <ehabkost@redhat.com> writes: > On Fri, Sep 04, 2020 at 04:54:21PM +0200, Vitaly Kuznetsov wrote: >> We have all the required data in X86CPU already and as we are about to >> split hyperv_handle_properties() into hyperv_expand_features()/ >> hyperv_fill_cpuids() we can remove the blind copy. The functional change >> is that QEMU won't pass CPUID leaves it doesn't currently know about >> to the guest but arguably this is a good change. > > Is it, though? Maybe we don't want it to be the default, but a > blind passthrough mode that copies all CPUID leaves would be > useful for testing new features. > We already have Hyper-V features which require extra work to get enabled (SynIC, EVMCS). Passing corresponding feature bits to guests without actually enabling these features in KVM will likely break them. So a pure 'blind passthrough' mode is not possible. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> --- >> target/i386/kvm.c | 9 --------- >> 1 file changed, 9 deletions(-) >> >> diff --git a/target/i386/kvm.c b/target/i386/kvm.c >> index 87b83a2aa2cb..b7f0e200a75f 100644 >> --- a/target/i386/kvm.c >> +++ b/target/i386/kvm.c >> @@ -1221,9 +1221,6 @@ static int hyperv_handle_properties(CPUState *cs, >> } >> >> if (cpu->hyperv_passthrough) { >> - memcpy(cpuid_ent, &cpuid->entries[0], >> - cpuid->nent * sizeof(cpuid->entries[0])); >> - >> c = cpuid_find_entry(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 0); >> if (c) { >> cpu->hyperv_vendor_id[0] = c->ebx; >> @@ -1325,12 +1322,6 @@ static int hyperv_handle_properties(CPUState *cs, >> goto free; >> } >> >> - if (cpu->hyperv_passthrough) { >> - /* We already copied all feature words from KVM as is */ >> - r = cpuid->nent; >> - goto free; >> - } >> - >> c = &cpuid_ent[cpuid_i++]; >> c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS; >> c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ? >> -- >> 2.25.4 >>
diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 87b83a2aa2cb..b7f0e200a75f 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -1221,9 +1221,6 @@ static int hyperv_handle_properties(CPUState *cs, } if (cpu->hyperv_passthrough) { - memcpy(cpuid_ent, &cpuid->entries[0], - cpuid->nent * sizeof(cpuid->entries[0])); - c = cpuid_find_entry(cpuid, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, 0); if (c) { cpu->hyperv_vendor_id[0] = c->ebx; @@ -1325,12 +1322,6 @@ static int hyperv_handle_properties(CPUState *cs, goto free; } - if (cpu->hyperv_passthrough) { - /* We already copied all feature words from KVM as is */ - r = cpuid->nent; - goto free; - } - c = &cpuid_ent[cpuid_i++]; c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS; c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ?
We have all the required data in X86CPU already and as we are about to split hyperv_handle_properties() into hyperv_expand_features()/ hyperv_fill_cpuids() we can remove the blind copy. The functional change is that QEMU won't pass CPUID leaves it doesn't currently know about to the guest but arguably this is a good change. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- target/i386/kvm.c | 9 --------- 1 file changed, 9 deletions(-)