CPUID is failing starting from 12-15 July

[9il]

CPUID library https://github.com/libmir/cpuid
is failing starting from 12-15 July.
Does appveyor use virtual machine without CPUID instruction support?

[FeodorFitsner]

How do you use CPUID?

[9il]

The exact problem is that for (virtual?) Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz

1. after CPUID(EAX<-0), registerEAX >= 0xB - this means that 0xB CPUID information leaf can be used.
2. after CPUID(EAX<-0xB, ECX<-0), register EBX[31..0] == 0 - this means that there are 0 threads per core. So, cores # (cores = threads / threadsPerCore) gives division by 0.

CpuInfo _cpuid(uint eax, uint ecx = 0)
{
    uint a = void;
    uint b = void;
    uint c = void;
    uint d = void;
        asm pure nothrow @nogc
        {
            mov EAX, eax;
            mov ECX, ecx;
            cpuid;
            mov a, EAX;
            mov b, EBX;
            mov c, ECX;
            mov d, EDX;
        }
    return CpuInfo(a, b, c, d);
}

I suppose that problem is in virtualisation. It can be checked on real E5-2680 v3:

dub fetch cpuid
dub test cpuid

where dub is D package manager.

[FeodorFitsner]

Right, builds are currently running on Hyper-V VMs. You would probably need to adjust your library to support such cases.

[9il]

Right, builds are currently running on Hyper-V VMs. You would probably need to adjust your library to support such cases.

This is not possible because vendor is specified as GenuineIntel. I can tune it if is Microsoft Hv.

Either vendor should be changed to Microsoft Hv or behaviour should be the same like GenuineIntel.

[dnadlinger]

Maybe this would be interesting for a workaround:

Software determines the presence of a hypervisor through the CPUID instruction. Processors conforming to the Intel® 64 architecture have reserved a feature flag in CPUID Function 0x01 - Feature Information for this purpose. Bit 31 returned in ECX is defined as Not Used, and will always return 0 from the physical CPU. A hypervisor conformant with the Microsoft hypervisor interface will set CPUID.1:ECX [bit 31] = 1 to indicate its presence to software.

[9il]

@klickverbot Thanks!