From: Avi Kivity <avi@redhat.com>
To: Glauber Costa <glommer@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/6] export new cpuid KVM_CAP
Date: Tue, 27 Apr 2010 22:20:52 +0300 [thread overview]
Message-ID: <4BD73914.8040209@redhat.com> (raw)
In-Reply-To: <20100427190901.GS16166@mothafucka.localdomain>
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.
next prev parent reply other threads:[~2010-04-27 19:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-26 17:46 [PATCH 0/6] pvclock fixes Glauber Costa
2010-04-26 17:46 ` [PATCH 1/6] Enable pvclock flags in vcpu_time_info structure Glauber Costa
2010-04-26 17:46 ` [PATCH 2/6] Add a global synchronization point for pvclock Glauber Costa
2010-04-26 17:46 ` [PATCH 3/6] change msr numbers for kvmclock Glauber Costa
2010-04-26 17:46 ` [PATCH 4/6] export new cpuid KVM_CAP Glauber Costa
2010-04-26 17:46 ` [PATCH 5/6] Try using new kvm clock msrs Glauber Costa
2010-04-26 17:46 ` [PATCH 6/6] don't compute pvclock adjustments if we trust the tsc Glauber Costa
2010-04-27 13:40 ` Marcelo Tosatti
2010-04-27 15:11 ` Glauber Costa
2010-04-27 18:03 ` Avi Kivity
2010-04-27 18:57 ` Glauber Costa
2010-04-27 13:35 ` [PATCH 5/6] Try using new kvm clock msrs Marcelo Tosatti
2010-04-27 13:30 ` [PATCH 4/6] export new cpuid KVM_CAP Marcelo Tosatti
2010-04-27 15:09 ` Glauber Costa
2010-04-27 16:55 ` Glauber Costa
2010-04-27 18:12 ` Avi Kivity
2010-04-27 19:09 ` Glauber Costa
2010-04-27 19:20 ` Avi Kivity [this message]
2010-04-27 13:28 ` [PATCH 2/6] Add a global synchronization point for pvclock Marcelo Tosatti
2010-04-27 18:00 ` Jeremy Fitzhardinge
2010-04-26 18:11 ` [PATCH 1/6] Enable pvclock flags in vcpu_time_info structure Jeremy Fitzhardinge
2010-04-26 18:45 ` Glauber Costa
2010-04-27 18:07 ` Avi Kivity
2010-04-27 19:09 ` Glauber Costa
2010-04-27 2:21 ` [PATCH 0/6] pvclock fixes Zachary Amsden
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