Re: [PATCH 1/5] i386: move hyperv_vendor_id initialization to x86_cpu_realizefn()

[Vitaly Kuznetsov]

Claudio Fontana <cfontana@suse.de> writes:

> On 11/19/20 11:32 AM, Vitaly Kuznetsov wrote:
>> As a preparation to expanding Hyper-V CPU features early, move
>> hyperv_vendor_id initialization to x86_cpu_realizefn(). Introduce
>> x86_cpu_hyperv_realize() to not not pollute x86_cpu_realizefn()
>> itself.
>> 
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>
>
> Hi Vitaly,
>
> If building for TCG-only, does the x86_cpu_hyperv_realize function and other 
> hyperv related functions
> make sense to keep in the build?
>
> Now that we have per-accelerator subdirs in target/i386, should the hyperv 
> code be moved over?
>

Hi Claudio,

I'm not exactly sure. On one hand, we only implement Hyper-V emulation
with KVM now. On the other hand Hyper-V specific CPU options are
available even without it (and as Igor feels strongly against
introducing custom option parsers, I don't see how we can forbid to use
them without KVM). x86_cpu_hyperv_realize() is the bare minimum which is
only needed to set our internal Hyper-V related data in a sane way,
e.g. set the default to 'cpu->hyperv_vendor_id'. The actual enablement
code is in target/i386/kvm.c already. Do you see anything besides
x86_cpu_hyperv_realize() which we could move there? Could you please
take a look at v5
(https://mail.gnu.org/archive/html/qemu-devel/2021-03/msg00158.html)?

Thanks!


> Thanks,
>
> Claudio
>
>
>> ---
>>  target/i386/cpu.c | 23 ++++++++++++++++++++++-
>>  target/i386/cpu.h |  3 ++-
>>  target/i386/kvm.c | 25 ++++++++++---------------
>>  3 files changed, 34 insertions(+), 17 deletions(-)
>> 
>> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>> index 5a8c96072e41..2a6885753378 100644
>> --- a/target/i386/cpu.c
>> +++ b/target/i386/cpu.c
>> @@ -6509,6 +6509,25 @@ static void x86_cpu_filter_features(X86CPU *cpu, bool 
>> verbose)
>>      }
>>  }
>>  
>> +static void x86_cpu_hyperv_realize(X86CPU *cpu)
>> +{
>> +    size_t len;
>> +
>> +    /* Hyper-V vendor id */
>> +    if (!cpu->hyperv_vendor) {
>> +        memcpy(cpu->hyperv_vendor_id, "Microsoft Hv", 12);
>> +    } else {
>> +        len = strlen(cpu->hyperv_vendor);
>> +
>> +        if (len > 12) {
>> +            warn_report("hv-vendor-id truncated to 12 characters");
>> +            len = 12;
>> +        }
>> +        memset(cpu->hyperv_vendor_id, 0, 12);
>> +        memcpy(cpu->hyperv_vendor_id, cpu->hyperv_vendor, len);
>> +    }
>> +}
>> +
>>  static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
>>  {
>>      CPUState *cs = CPU(dev);
>> @@ -6680,6 +6699,8 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
>> **errp)
>>          env->cache_info_amd.l3_cache = &legacy_l3_cache;
>>      }
>>  
>> +    /* Process Hyper-V enlightenments */
>> +    x86_cpu_hyperv_realize(cpu);
>>  
>>      cpu_exec_realizefn(cs, &local_err);
>>      if (local_err != NULL) {
>> @@ -7198,7 +7219,7 @@ static Property x86_cpu_properties[] = {
>>      DEFINE_PROP_UINT32("min-xlevel2", X86CPU, env.cpuid_min_xlevel2, 0),
>>      DEFINE_PROP_UINT64("ucode-rev", X86CPU, ucode_rev, 0),
>>      DEFINE_PROP_BOOL("full-cpuid-auto-level", X86CPU, 
>> full_cpuid_auto_level, true),
>> -    DEFINE_PROP_STRING("hv-vendor-id", X86CPU, hyperv_vendor_id),
>> +    DEFINE_PROP_STRING("hv-vendor-id", X86CPU, hyperv_vendor),
>>      DEFINE_PROP_BOOL("cpuid-0xb", X86CPU, enable_cpuid_0xb, true),
>>      DEFINE_PROP_BOOL("lmce", X86CPU, enable_lmce, false),
>>      DEFINE_PROP_BOOL("l3-cache", X86CPU, enable_l3_cache, true),
>> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
>> index 88e8586f8fb4..be640bf45c29 100644
>> --- a/target/i386/cpu.h
>> +++ b/target/i386/cpu.h
>> @@ -1655,11 +1655,12 @@ struct X86CPU {
>>      uint64_t ucode_rev;
>>  
>>      uint32_t hyperv_spinlock_attempts;
>> -    char *hyperv_vendor_id;
>> +    char *hyperv_vendor;
>>      bool hyperv_synic_kvm_only;
>>      uint64_t hyperv_features;
>>      bool hyperv_passthrough;
>>      OnOffAuto hyperv_no_nonarch_cs;
>> +    uint32_t hyperv_vendor_id[3];
>>  
>>      bool check_cpuid;
>>      bool enforce_cpuid;
>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
>> index a2934dda027c..788a2cf2ec51 100644
>> --- a/target/i386/kvm.c
>> +++ b/target/i386/kvm.c
>> @@ -1205,6 +1205,13 @@ static int hyperv_handle_properties(CPUState *cs,
>>          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;
>> +            cpu->hyperv_vendor_id[1] = c->ecx;
>> +            cpu->hyperv_vendor_id[2] = c->edx;
>> +        }
>> +
>>          c = cpuid_find_entry(cpuid, HV_CPUID_FEATURES, 0);
>>          if (c) {
>>              env->features[FEAT_HYPERV_EAX] = c->eax;
>> @@ -1279,23 +1286,11 @@ static int hyperv_handle_properties(CPUState *cs,
>>  
>>      c = &cpuid_ent[cpuid_i++];
>>      c->function = HV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
>> -    if (!cpu->hyperv_vendor_id) {
>> -        memcpy(signature, "Microsoft Hv", 12);
>> -    } else {
>> -        size_t len = strlen(cpu->hyperv_vendor_id);
>> -
>> -        if (len > 12) {
>> -            error_report("hv-vendor-id truncated to 12 characters");
>> -            len = 12;
>> -        }
>> -        memset(signature, 0, 12);
>> -        memcpy(signature, cpu->hyperv_vendor_id, len);
>> -    }
>>      c->eax = hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) ?
>>          HV_CPUID_NESTED_FEATURES : HV_CPUID_IMPLEMENT_LIMITS;
>> -    c->ebx = signature[0];
>> -    c->ecx = signature[1];
>> -    c->edx = signature[2];
>> +    c->ebx = cpu->hyperv_vendor_id[0];
>> +    c->ecx = cpu->hyperv_vendor_id[1];
>> +    c->edx = cpu->hyperv_vendor_id[2];
>>  
>>      c = &cpuid_ent[cpuid_i++];
>>      c->function = HV_CPUID_INTERFACE;
>> 
>

-- 
Vitaly