Re: [Qemu-devel] [PATCH 2/2] target-i386: Fix default Hypervisor level for hypervisor-vendor=kvm.

[Don Slutz <Don@CloudSwitch.Com>]

On 09/19/12 09:20, Eduardo Habkost wrote:
> On Tue, Sep 18, 2012 at 03:32:04PM -0400, Don Slutz wrote:
>> On 09/18/12 13:00, Eduardo Habkost wrote:
>>> On Tue, Sep 18, 2012 at 10:49:53AM -0400, Don Slutz wrote:
>>>>  From http://lkml.indiana.edu/hypermail/linux/kernel/1205.0/00100.html
>>>> EAX should be KVM_CPUID_FEATURES (0x40000001) not 0.
>>>>
>>>> If kvm is not configured, the additional option of hypervisor-level=1
>>>> (or hypervisor-level=0x40000001) needs to be specified to get this.
>>>> ---
>>>>   target-i386/cpu.c |   12 +++++++++++-
>>>>   1 files changed, 11 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
>>>> index 6e43eff..d73b0a8 100644
>>>> --- a/target-i386/cpu.c
>>>> +++ b/target-i386/cpu.c
>>>> @@ -1248,7 +1248,12 @@ static char *x86_cpuid_get_hv_vendor(Object *obj, Error **errp)
>>>>                  env->cpuid_hv_level == CPUID_HV_LEVEL_XEN) {
>>>>           pstrcpy(value, sizeof(value), "xen");
>>>>       } else if (!strcmp(value, CPUID_HV_VENDOR_KVM) &&
>>>> -               env->cpuid_hv_level == 0) {
>>>> +#if defined(CONFIG_KVM)
>>>> +               env->cpuid_hv_level == KVM_CPUID_FEATURES
>>>> +#else
>>>> +               env->cpuid_hv_level == 0
>>>> +#endif
>>>> +	    ) {
>>>>           pstrcpy(value, sizeof(value), "kvm");
>>>>       }
>>>>       return value;
>>>> @@ -1281,6 +1286,11 @@ static void x86_cpuid_set_hv_vendor(Object *obj, const char *value,
>>>>           }
>>>>           pstrcpy(adj_value, sizeof(adj_value), CPUID_HV_VENDOR_XEN);
>>>>       } else if (!strcmp(value, "kvm")) {
>>>> +#if defined(CONFIG_KVM)
>>>> +        if (env->cpuid_hv_level == 0) {
>>>> +            env->cpuid_hv_level = KVM_CPUID_FEATURES;
>>>> +        }
>>>> +#endif
>>> If CPUID[0x40000000].EAX set to 0 is documented as equivalent to having
>>> it set to 0x40000001 (KVM_CPUID_FEATURES), why the confusing checks for
>>> CONFIG_KVM? Why not always set it to KVM_CPUID_FEATURES?
>>>
>> At line 36 of the file:
>>
>> #if defined(CONFIG_KVM)
>> #include <linux/kvm_para.h>
>> #endif
>>
>> So without the check you get compile failures (i386-linux-user).
>>
> Right. We can't include linux/kvm_para.h on a non-Linux build host, but
> on the other hand I don't see any reason to not have
> cpuid_hv_level=0x40000001 on builds without CONFIG_KVM too.
>
> If we want to allow fake KVM CPUID leaves on non-CONFIG_KVM builds like
> the code above does, QEMU needs its own constant for
> KVM_CPUID_FEATURES/0x40000001, so it doesn't depend on the Linux header.
>
Will do a V2 with a local define.
>> I have no issue with removing the check(s) for 0.  Currently
>> hypervisor-level=0 will not force the old values; I can make a change
>> so that works.
>>       -Don Slutz
   -Don Slutz