From: Glauber Costa <glommer@parallels.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>, <kvm@vger.kernel.org>,
<johnstul@us.ibm.com>, <zamsden@gmail.com>, <gleb@redhat.com>,
<avi@redhat.com>, <pbonzini@redhat.com>
Subject: Re: [patch 09/18] KVM: x86: introduce facility to support vsyscall pvclock, via MSR
Date: Tue, 30 Oct 2012 11:38:20 +0400 [thread overview]
Message-ID: <508F83EC.4050007@parallels.com> (raw)
In-Reply-To: <508EC089.5030409@goop.org>
On 10/29/2012 09:44 PM, Jeremy Fitzhardinge wrote:
> On 10/29/2012 07:45 AM, Glauber Costa wrote:
>> On 10/24/2012 05:13 PM, Marcelo Tosatti wrote:
>>> Allow a guest to register a second location for the VCPU time info
>>>
>>> structure for each vcpu (as described by MSR_KVM_SYSTEM_TIME_NEW).
>>> This is intended to allow the guest kernel to map this information
>>> into a usermode accessible page, so that usermode can efficiently
>>> calculate system time from the TSC without having to make a syscall.
>>>
>>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>> Can you please be a bit more specific about why we need this? Why does
>> the host need to provide us with two pages with the exact same data? Why
>> can't just do it with mapping tricks in the guest?
>
> In Xen the pvclock structure is embedded within a pile of other stuff
> that shouldn't be mapped into guest memory, so providing for a second
> location allows it to be placed whereever is convenient for the guest.
> That's a restriction of the Xen ABI, but I don't know if it affects KVM.
>
> J
>
In kvm the exported data seems to be exactly the same. So it makes sense
to have a single page exported to the guest. The guest may have a
facility that maps the vsyscall clock and the normal clock to a specific
location given a page - that can be either a different page or the same
page.
Any reason why it wouldn't work?
next prev parent reply other threads:[~2012-10-30 7:38 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 13:13 [patch 00/18] pvclock vsyscall support + KVM hypervisor support (v2) Marcelo Tosatti
2012-10-24 13:13 ` [patch 01/18] KVM: x86: retain pvclock guest stopped bit in guest memory Marcelo Tosatti
2012-10-24 13:13 ` [patch 02/18] x86: pvclock: make sure rdtsc doesnt speculate out of region Marcelo Tosatti
2012-10-24 13:13 ` [patch 03/18] x86: pvclock: remove pvclock_shadow_time Marcelo Tosatti
2012-10-30 9:23 ` Avi Kivity
2012-10-30 9:24 ` Avi Kivity
2012-10-24 13:13 ` [patch 04/18] x86: pvclock: create helper for pvclock data retrieval Marcelo Tosatti
2012-10-24 13:13 ` [patch 05/18] x86: pvclock: fix flags usage race Marcelo Tosatti
2012-10-24 13:13 ` [patch 06/18] x86: pvclock: introduce helper to read flags Marcelo Tosatti
2012-10-24 13:13 ` [patch 07/18] sched: add notifier for cross-cpu migrations Marcelo Tosatti
2012-10-24 13:13 ` [patch 08/18] x86: pvclock: generic pvclock vsyscall initialization Marcelo Tosatti
2012-10-29 14:18 ` Glauber Costa
2012-10-29 14:54 ` Marcelo Tosatti
2012-10-29 17:46 ` Jeremy Fitzhardinge
2012-10-29 14:39 ` Glauber Costa
2012-10-24 13:13 ` [patch 09/18] KVM: x86: introduce facility to support vsyscall pvclock, via MSR Marcelo Tosatti
2012-10-29 14:45 ` Glauber Costa
2012-10-29 17:44 ` Jeremy Fitzhardinge
2012-10-29 18:40 ` Marcelo Tosatti
2012-10-30 7:41 ` Glauber Costa
2012-10-30 9:39 ` Avi Kivity
2012-10-31 3:12 ` Marcelo Tosatti
2012-11-02 10:21 ` Glauber Costa
2012-10-30 7:38 ` Glauber Costa [this message]
2012-10-24 13:13 ` [patch 10/18] x86: kvm guest: pvclock vsyscall support Marcelo Tosatti
2012-10-24 13:13 ` [patch 11/18] x86: vsyscall: pass mode to gettime backend Marcelo Tosatti
2012-10-29 14:47 ` Glauber Costa
2012-10-29 18:41 ` Marcelo Tosatti
2012-10-30 7:42 ` Glauber Costa
2012-10-24 13:13 ` [patch 12/18] x86: vdso: pvclock gettime support Marcelo Tosatti
2012-10-29 14:59 ` Glauber Costa
2012-10-29 18:42 ` Marcelo Tosatti
2012-10-30 7:49 ` Glauber Costa
2012-10-31 3:16 ` Marcelo Tosatti
2012-10-24 13:13 ` [patch 13/18] KVM: x86: pass host_tsc to read_l1_tsc Marcelo Tosatti
2012-10-29 15:04 ` Glauber Costa
2012-10-29 18:45 ` Marcelo Tosatti
2012-10-30 7:55 ` Glauber Costa
2012-10-24 13:13 ` [patch 14/18] time: export time information for KVM pvclock Marcelo Tosatti
2012-11-10 1:02 ` John Stultz
2012-11-13 21:07 ` Marcelo Tosatti
2012-10-24 13:13 ` [patch 15/18] KVM: x86: implement PVCLOCK_TSC_STABLE_BIT pvclock flag Marcelo Tosatti
2012-10-30 8:34 ` Glauber Costa
2012-10-31 3:19 ` [patch 15/18] KVM: x86: implement PVCLOCK_TSC_STABLE_BIT pvclock flag\ Marcelo Tosatti
2012-10-24 13:13 ` [patch 16/18] KVM: x86: notifier for clocksource changes Marcelo Tosatti
2012-10-24 13:13 ` [patch 17/18] KVM: x86: add kvm_arch_vcpu_postcreate callback, move TSC initialization Marcelo Tosatti
2012-10-24 13:13 ` [patch 18/18] KVM: x86: require matched TSC offsets for master clock Marcelo Tosatti
2012-10-31 22:46 ` [patch 00/16] pvclock vsyscall support + KVM hypervisor support (v3) Marcelo Tosatti
2012-10-31 22:46 ` [patch 01/16] KVM: x86: retain pvclock guest stopped bit in guest memory Marcelo Tosatti
2012-11-01 10:39 ` Gleb Natapov
2012-11-01 20:51 ` Marcelo Tosatti
2012-11-01 13:44 ` Glauber Costa
2012-10-31 22:46 ` [patch 02/16] x86: pvclock: make sure rdtsc doesnt speculate out of region Marcelo Tosatti
2012-11-01 11:48 ` Gleb Natapov
2012-11-01 13:49 ` Glauber Costa
2012-11-01 13:51 ` Gleb Natapov
2012-11-01 20:56 ` Marcelo Tosatti
2012-11-01 22:13 ` Gleb Natapov
2012-11-01 22:21 ` Marcelo Tosatti
2012-11-02 6:02 ` Gleb Natapov
2012-10-31 22:46 ` [patch 03/16] x86: pvclock: remove pvclock_shadow_time Marcelo Tosatti
2012-11-01 13:52 ` Glauber Costa
2012-10-31 22:47 ` [patch 04/16] x86: pvclock: create helper for pvclock data retrieval Marcelo Tosatti
2012-11-01 14:04 ` Glauber Costa
2012-11-01 20:57 ` Marcelo Tosatti
2012-10-31 22:47 ` [patch 05/16] x86: pvclock: introduce helper to read flags Marcelo Tosatti
2012-11-01 14:07 ` Glauber Costa
2012-11-01 21:08 ` Marcelo Tosatti
2012-10-31 22:47 ` [patch 06/16] sched: add notifier for cross-cpu migrations Marcelo Tosatti
2012-11-01 14:08 ` Glauber Costa
2012-10-31 22:47 ` [patch 07/16] x86: pvclock: generic pvclock vsyscall initialization Marcelo Tosatti
2012-11-01 14:19 ` Glauber Costa
2012-10-31 22:47 ` [patch 08/16] KVM: x86: introduce facility to support vsyscall pvclock, via MSR Marcelo Tosatti
2012-11-01 14:28 ` Glauber Costa
2012-11-01 21:39 ` Marcelo Tosatti
2012-11-02 10:23 ` Glauber Costa
2012-11-02 13:00 ` Marcelo Tosatti
2012-11-05 8:03 ` Glauber Costa
2012-10-31 22:47 ` [patch 09/16] x86: kvm guest: pvclock vsyscall support Marcelo Tosatti
2012-11-02 9:42 ` Glauber Costa
2012-11-05 8:35 ` Marcelo Tosatti
2012-10-31 22:47 ` [patch 10/16] x86: vdso: pvclock gettime support Marcelo Tosatti
2012-11-01 14:41 ` Glauber Costa
2012-11-01 21:42 ` Marcelo Tosatti
2012-11-02 0:33 ` Marcelo Tosatti
2012-11-02 10:25 ` Glauber Costa
2012-11-14 10:42 ` Gleb Natapov
2012-11-14 22:42 ` Marcelo Tosatti
2012-10-31 22:47 ` [patch 11/16] KVM: x86: pass host_tsc to read_l1_tsc Marcelo Tosatti
2012-10-31 22:47 ` [patch 12/16] time: export time information for KVM pvclock Marcelo Tosatti
2012-10-31 22:47 ` [patch 13/16] KVM: x86: implement PVCLOCK_TSC_STABLE_BIT pvclock flag Marcelo Tosatti
2012-10-31 22:47 ` [patch 14/16] KVM: x86: notifier for clocksource changes Marcelo Tosatti
2012-10-31 22:47 ` [patch 15/16] KVM: x86: add kvm_arch_vcpu_postcreate callback, move TSC initialization Marcelo Tosatti
2012-10-31 22:47 ` [patch 16/16] KVM: x86: require matched TSC offsets for master clock Marcelo Tosatti
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