From: Gleb Natapov <gleb@redhat.com>
To: "Nadav Har'El" <nyh@math.technion.ac.il>
Cc: Avi Kivity <avi@redhat.com>,
Stefan Bader <stefan.bader@canonical.com>,
kvm@vger.kernel.org, Andy Whitcroft <apw@canonical.com>
Subject: Re: Nested kvm_intel broken on pre 3.3 hosts
Date: Wed, 1 Aug 2012 18:10:20 +0300 [thread overview]
Message-ID: <20120801151020.GE27579@redhat.com> (raw)
In-Reply-To: <20120801150707.GA3688@fermat.math.technion.ac.il>
On Wed, Aug 01, 2012 at 06:07:07PM +0300, Nadav Har'El wrote:
> On Wed, Aug 01, 2012, Avi Kivity wrote about "Re: Nested kvm_intel broken on pre 3.3 hosts":
> > Right - it's not just kvm-as-a-guest that will trip on this. But
> > there's no point in everyone backporting it on their own. If you're
> > doing the backport, please post it here and we'll forward it to the
> > stable branch.
>
> If I understand correctly, the failure occurs because new versions of
> KVM refuse to work if the processor doesn't support CPU_BASED_RDPMC_EXITING -
> which older versions of nested VMX didn't say that they did.
>
> But must the KVM guest refuse to work if this feature isn't supported?
> I.e., why not move in setup_vmcs_config() the CPU_BASED_RDPMC_EXITING
> from "min" to "opt"? Isn't losing the PMU feature a lesser evil than
> not working at all? In any case, perhaps the original reporter can use
> this as a workaround, at least, because it requires modifying the (L1)
> guest, not the host.
>
>
Since L2 or L1 have to be fixed anyway for setup to work it is better to
fix L1 to work according to a spec than fixing L2 to workaround L1 bug.
--
Gleb.
next prev parent reply other threads:[~2012-08-01 15:10 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-01 11:29 Nested kvm_intel broken on pre 3.3 hosts Stefan Bader
2012-08-01 13:39 ` Gleb Natapov
2012-08-01 14:08 ` Avi Kivity
2012-08-01 14:26 ` Stefan Bader
2012-08-01 14:29 ` Avi Kivity
2012-08-01 15:07 ` Nadav Har'El
2012-08-01 15:10 ` Gleb Natapov [this message]
2012-08-01 15:11 ` Avi Kivity
2012-08-02 15:19 ` Stefan Bader
2012-08-02 15:19 ` [PATCH 1/7] KVM: Move cpuid code to new file Stefan Bader
2012-08-02 15:19 ` [PATCH 2/7] KVM: expose latest Intel cpu new features (BMI1/BMI2/FMA/AVX2) to guest Stefan Bader
2012-08-02 15:19 ` [PATCH 3/7] KVM: Expose kvm_lapic_local_deliver() Stefan Bader
2012-08-02 15:19 ` [PATCH 4/7] KVM: Expose a version 2 architectural PMU to a guests Stefan Bader
2012-08-02 15:19 ` [PATCH 5/7] KVM: Add generic RDPMC support Stefan Bader
2012-08-02 15:19 ` [PATCH 6/7] KVM: SVM: Intercept RDPMC Stefan Bader
2012-08-02 15:19 ` [PATCH 7/7] KVM: VMX: " Stefan Bader
2012-08-02 15:26 ` Nested kvm_intel broken on pre 3.3 hosts Avi Kivity
2012-08-03 10:55 ` (unknown), Stefan Bader
2012-08-03 10:57 ` Nested kvm_intel broken on pre 3.3 hosts Stefan Bader
2012-08-05 9:18 ` Avi Kivity
2012-08-06 14:40 ` Stefan Bader
2012-08-09 7:13 ` Stefan Bader
2012-08-09 9:34 ` Avi Kivity
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