From: Zachary Amsden <zamsden@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Avi Kivity <avi@redhat.com>, Joerg Roedel <joerg.roedel@amd.com>,
kvm <kvm@vger.kernel.org>
Subject: Re: Nested SVM and migration
Date: Mon, 22 Feb 2010 06:46:19 -1000 [thread overview]
Message-ID: <4B82B4DB.1090703@redhat.com> (raw)
In-Reply-To: <20100221130915.GB26465@8bytes.org>
On 02/21/2010 03:09 AM, Joerg Roedel wrote:
> On Sun, Feb 21, 2010 at 02:54:01PM +0200, Avi Kivity wrote:
>
>> So, if some other cpu (or the guest itself, with appropriate
>> permissions) modifies the msr permission bitmap, svm will not notice
>> this? svm loads the bitmap during entry?
>>
> Yes.
>
Ugh. So we have non-reversible architectural state all over again.
There are ways around this problem, all ugly, but the easiest is
shadowing the MSR permission bitmap.
>> I don't think you can tell, unless the host cpu modifying the vmcb is
>> synchronized with the guest (or the guest modifies its own vmcb). But
>> this is all academic.
>>
> Hmm, another thing comes to mind. We would need some redesign of the
> nested_svm code to allow userspace to put a vcpu directly into nested
> state. With the MSR approach, all userspace does is to write MSRs into
> the vcpu before the first run?
>
How does MSR_KVM_NESTED_SVM_ACTIVE not solve this problem?
next prev parent reply other threads:[~2010-02-22 16:46 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-20 19:14 Nested SVM and migration Zachary Amsden
2010-02-20 20:18 ` Joerg Roedel
2010-02-20 23:26 ` Zachary Amsden
2010-02-21 12:10 ` Joerg Roedel
2010-02-21 12:24 ` Avi Kivity
2010-02-21 12:41 ` Joerg Roedel
2010-02-21 12:54 ` Avi Kivity
2010-02-21 13:09 ` Joerg Roedel
2010-02-21 13:14 ` Avi Kivity
[not found] ` <4B8137E7.4030001@redhat.com>
[not found] ` <20100221144352.GC26465@8bytes.org>
2010-02-22 16:54 ` Zachary Amsden
[not found] ` <4B814C41.7010105@redhat.com>
[not found] ` <20100221155624.GD26465@8bytes.org>
2010-02-22 16:56 ` Zachary Amsden
2010-02-22 16:59 ` Avi Kivity
2010-02-22 16:46 ` Zachary Amsden [this message]
2010-02-22 17:07 ` Joerg Roedel
2010-02-24 15:23 ` Joerg Roedel
2010-02-24 20:21 ` Zachary Amsden
2010-02-22 16:42 ` Zachary Amsden
2010-02-22 16:44 ` Avi Kivity
2010-02-22 17:00 ` Zachary Amsden
2010-02-22 17:02 ` Avi Kivity
2010-02-22 17:07 ` Zachary Amsden
2010-02-22 17:11 ` Avi Kivity
2010-02-22 17:24 ` Zachary Amsden
2010-02-22 16:39 ` Zachary Amsden
2010-02-21 7:23 ` Avi Kivity
2010-02-21 7:46 ` Gleb Natapov
2010-02-21 8:12 ` Avi Kivity
2010-02-21 12:18 ` Joerg Roedel
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