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SubjectRe: [PATCH 4/6] export new cpuid KVM_CAP
On 04/27/2010 10:09 PM, Glauber Costa wrote:
>> Hmm. We already have an API to get cpuid bits:
>> KVM_GET_SUPPORTED_CPUID2. The nice thing about it is that it will
>> mean -cpu host will work out of the box.
> Ok, from what I understand, KVM_GET_CPUID2 gets a set of features, and tells
> userspace which of them are available. Right?

No. KVM_GET_CPUID2 reads what was set by KVM_SET_CPUID, as modified by
the guest executing the cpuid instruction. KVM_GET_SUPPORTED_CPUID
tells userspace which bits are supported by the host cpu and kvm.

> If this is the case, userspace could ask for 0xffffffff, and then we tell them
> which of them are present.
> Does that make sense?

The API for KVM_GET_SUPPORTED_CPUID returns all cpuid leaves supported
in one go, IIRC.

Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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