From: Avi Kivity <avi@redhat.com>
To: Glauber Costa <glommer@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Rik van Riel <riel@redhat.com>,
Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
Peter Zijlstra <peterz@infradead.org>,
Anthony Liguori <aliguori@us.ibm.com>,
Eric B Munson <emunson@mgebm.net>
Subject: Re: [PATCH v5 4/9] KVM-HV: KVM Steal time implementation
Date: Mon, 11 Jul 2011 15:58:18 +0300 [thread overview]
Message-ID: <4E1AF36A.2060605@redhat.com> (raw)
In-Reply-To: <4E15E7E5.6020909@redhat.com>
On 07/07/2011 08:07 PM, Glauber Costa wrote:
>>> +static void record_steal_time(struct kvm_vcpu *vcpu)
>>> +{
>>> + u64 delta;
>>> +
>>> + if (!(vcpu->arch.st.msr_val& KVM_MSR_ENABLED))
>>> + return;
>>> +
>>> + if (unlikely(kvm_read_guest_cached(vcpu->kvm,&vcpu->arch.st.stime,
>>> + &vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
>>> + return;
>>
>> The guest memory page is not pinned, sleeping via
>> __copy_from_user/to_user is not allowed in vcpu_load context. Either pin
>> it or use atomic acessors.
>
>
> I do recognize the problem.
> Avi, what's your take here?
>
The easiest solution is to set a KVM_REQ bit in atomic context, and move
the sleepy code to vcpu_enter_guest().
>>> + case MSR_KVM_STEAL_TIME:
>>> + vcpu->arch.st.msr_val = data;
>>> +
>>> + if (!(data& KVM_MSR_ENABLED)) {
>>> + break;
>>> + }
>>
>> On failure below this point, msr_val should be cleared of
>> KVM_MSR_ENABLED?
> No, msr_val has to hold whatever the guest wrote into it.
> We should probably use an independent variable here to indicate that
> we failed to activate it.
If we fail, we return a #GP to the guest (and don't write any value into
the msr).
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2011-07-11 12:58 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-04 15:32 [PATCH v5 0/9] Steal time for KVM Glauber Costa
2011-07-04 15:32 ` [PATCH v5 1/9] introduce kvm_read_guest_cached Glauber Costa
2011-07-05 19:35 ` Eric B Munson
2011-07-06 3:45 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 2/9] KVM-HDR Add constant to represent KVM MSRs enabled bit Glauber Costa
2011-07-05 19:36 ` Eric B Munson
2011-07-06 3:45 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 3/9] KVM-HDR: KVM Steal time implementation Glauber Costa
2011-07-05 19:36 ` Eric B Munson
2011-07-06 3:46 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 4/9] KVM-HV: " Glauber Costa
2011-07-05 19:36 ` Eric B Munson
2011-07-06 16:08 ` Rik van Riel
2011-07-07 10:51 ` Marcelo Tosatti
2011-07-07 17:07 ` Glauber Costa
2011-07-11 12:58 ` Avi Kivity [this message]
2011-07-11 14:05 ` Glauber Costa
2011-07-11 13:10 ` Avi Kivity
2011-07-11 13:11 ` Avi Kivity
2011-07-11 13:19 ` Glauber Costa
2011-07-04 15:32 ` [PATCH v5 5/9] KVM-GST: Add a pv_ops stub for steal time Glauber Costa
2011-07-05 19:36 ` Eric B Munson
2011-07-06 16:12 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 6/9] add jump labels for ia64 paravirt Glauber Costa
2011-07-05 19:36 ` Eric B Munson
2011-07-06 16:35 ` Rik van Riel
2011-07-11 13:09 ` Avi Kivity
2011-07-11 13:24 ` Glauber Costa
2011-07-11 14:15 ` Isaku Yamahata
2011-07-13 18:01 ` Luck, Tony
2011-07-04 15:32 ` [PATCH v5 7/9] KVM-GST: KVM Steal time accounting Glauber Costa
2011-07-05 9:11 ` Peter Zijlstra
2011-07-05 19:37 ` Eric B Munson
2011-07-06 16:37 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 8/9] KVM-GST: adjust scheduler cpu power Glauber Costa
2011-07-05 9:12 ` Peter Zijlstra
2011-07-05 19:37 ` Eric B Munson
2011-07-06 17:40 ` Rik van Riel
2011-07-04 15:32 ` [PATCH v5 9/9] KVM-GST: KVM Steal time registration Glauber Costa
2011-07-05 19:37 ` Eric B Munson
2011-07-06 17:42 ` Rik van Riel
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