Re: [Qemu-devel] [PATCH] WHPX Add signature CPUID

[Alessandro Pilotti]

Hi Paolo,

The main reason for different signatures is to allow guest workloads to be 
aware of the differences between the two platforms (eg VirtIO vs VMBus).

Thanks,

Alessandro

> On 15 May 2018, at 16:44, Paolo Bonzini <address@hidden> wrote:
> 
>> On 15/05/2018 13:37, address@hidden wrote:
>> From: Lucian Petrut <address@hidden>
>> 
>> Adds the CPUID trap for CPUID 0x40000000, sending the WHPX signature
>> to the guest upon request. This is consistent with other QEMU
>> accelerators (KVM).
>> 
>> Signed-off-by: Alessandro Pilotti <address@hidden>
>> Signed-off-by: Justin Terry (VM) <address@hidden>
>> Signed-off-by: Lucian Petrut <address@hidden>
> 
> Is it worth defining a different signature?  Can WHPX implement part of
> the Hyper-V spec, and if so would it be better to return the Hv
> signature ("Hv#1") instead?
> 
> Thanks,
> 
> Paolo
> 
>> ---
>> As opposed to the previous patch, this one will set the result of
>> this specific CPUID leaf when initializing the accelerator so that
>> we avoid a vcpu exit.
>> 
>> target/i386/whpx-all.c | 23 +++++++++++++++++++++++
>> 1 file changed, 23 insertions(+)
>> 
>> diff --git a/target/i386/whpx-all.c b/target/i386/whpx-all.c
>> index 5843517..c8310de 100644
>> --- a/target/i386/whpx-all.c
>> +++ b/target/i386/whpx-all.c
>> @@ -29,6 +29,8 @@
>> #include <WinHvPlatform.h>
>> #include <WinHvEmulation.h>
>> 
>> +#define WHPX_CPUID_SIGNATURE 0x40000000
>> +
>> struct whpx_state {
>>     uint64_t mem_quota;
>>     WHV_PARTITION_HANDLE partition;
>> @@ -1342,6 +1344,27 @@ static int whpx_accel_init(MachineState *ms)
>>                                  cpuidExitList,
>>                                  RTL_NUMBER_OF(cpuidExitList) * 
>> sizeof(UINT32));
>> 
>> +    UINT32 signature[3] = {0};
>> +    memcpy(signature, "WHPXWHPXWHPX", 12);
>> +
>> +    WHV_X64_CPUID_RESULT cpuidResultList[1] = {0};
>> +    cpuidResultList[0].Function = WHPX_CPUID_SIGNATURE;
>> +    cpuidResultList[0].Eax = 0;
>> +    cpuidResultList[0].Ebx = signature[0];
>> +    cpuidResultList[0].Ecx = signature[1];
>> +    cpuidResultList[0].Edx = signature[2];
>> +    hr = WHvSetPartitionProperty(whpx->partition,
>> +                                 WHvPartitionPropertyCodeCpuidResultList,
>> +                                 cpuidResultList,
>> +                                 RTL_NUMBER_OF(cpuidResultList) *
>> +                                    sizeof(WHV_X64_CPUID_RESULT));
>> +    if (FAILED(hr)) {
>> +        error_report("WHPX: Failed to set partition CpuidResultList 
>> hr=%08lx",
>> +                     hr);
>> +        ret = -EINVAL;
>> +        goto error;
>> +    }
>> +
>>     if (FAILED(hr)) {
>>         error_report("WHPX: Failed to set partition CpuidExitList hr=%08lx",
>>                      hr);
>> 
>