From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
Jan Kiszka <jan.kiszka@siemens.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
Xen <xen-devel@lists.xensource.com>,
Dave Jiang <dave.jiang@intel.com>, KVM <kvm@vger.kernel.org>,
Glauber Costa <glommer@redhat.com>, X86 <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Sasha Levin <levinsasha928@gmail.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Virtualization <virtualization@lists.linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Suzuki Poulo
Subject: Re: [PATCH RFC V4 4/5] kvm : pv-ticketlocks support for linux guests running on KVM hypervisor
Date: Wed, 25 Jan 2012 00:21:55 +0530 [thread overview]
Message-ID: <4F1EFDCB.5040808@linux.vnet.ibm.com> (raw)
In-Reply-To: <4F1EBB73.3000705@redhat.com>
On 01/24/2012 07:38 PM, Avi Kivity wrote:
> On 01/18/2012 11:52 PM, Jeremy Fitzhardinge wrote:
>> On 01/19/2012 12:54 AM, Srivatsa Vaddagiri wrote:
>>>
>>>> That logic relies on the "kick" being level triggered, so that "kick"
>>>> before "block" will cause the block to fall out immediately. If you're
>>>> using "hlt" as the block and it has the usual edge-triggered behaviour,
>>>> what stops a "kick-before-hlt" from losing the kick?
>>> Hmm ..'hlt' should result in a check for kick request (in hypervisor
>>> context) before vcpu is put to sleep. IOW vcpu1 that is attempting to kick vcpu0
>>> will set a 'somebody_tried_kicking_vcpu0' flag, which hypervisor should check
>>> before it puts vcpu0 to sleep because of trapped 'hlt' instruction.
>>>
>>> Won't that trap the 'kick-before-hlt' case? What am I missing here?
>>
>> Nothing, that sounds fine. It wasn't clear to me that your kick
>> operation left persistent state, and so has a level-triggered effect on hlt.
>>
>
> btw, this persistent state needs to be saved/restored for live
> migration. Best to put it into some MSR.
>
I did not quite get it. Did you mean, add a new MSR to msrs_to_save[],
and may be retain only the kicked/pv_unhalt flag (persistent state) and
get rid of PVLOCK_KICK vcpu->request?
WARNING: multiple messages have this Message-ID (diff)
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
Jan Kiszka <jan.kiszka@siemens.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Paul Mackerras <paulus@samba.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
Xen <xen-devel@lists.xensource.com>,
Dave Jiang <dave.jiang@intel.com>, KVM <kvm@vger.kernel.org>,
Glauber Costa <glommer@redhat.com>, X86 <x86@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Rik van Riel <riel@redhat.com>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Sasha Levin <levinsasha928@gmail.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Virtualization <virtualization@lists.linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Dave Hansen <dave@linux.vnet.ibm.com>,
Suzuki
Subject: Re: [PATCH RFC V4 4/5] kvm : pv-ticketlocks support for linux guests running on KVM hypervisor
Date: Wed, 25 Jan 2012 00:21:55 +0530 [thread overview]
Message-ID: <4F1EFDCB.5040808@linux.vnet.ibm.com> (raw)
In-Reply-To: <4F1EBB73.3000705@redhat.com>
On 01/24/2012 07:38 PM, Avi Kivity wrote:
> On 01/18/2012 11:52 PM, Jeremy Fitzhardinge wrote:
>> On 01/19/2012 12:54 AM, Srivatsa Vaddagiri wrote:
>>>
>>>> That logic relies on the "kick" being level triggered, so that "kick"
>>>> before "block" will cause the block to fall out immediately. If you're
>>>> using "hlt" as the block and it has the usual edge-triggered behaviour,
>>>> what stops a "kick-before-hlt" from losing the kick?
>>> Hmm ..'hlt' should result in a check for kick request (in hypervisor
>>> context) before vcpu is put to sleep. IOW vcpu1 that is attempting to kick vcpu0
>>> will set a 'somebody_tried_kicking_vcpu0' flag, which hypervisor should check
>>> before it puts vcpu0 to sleep because of trapped 'hlt' instruction.
>>>
>>> Won't that trap the 'kick-before-hlt' case? What am I missing here?
>>
>> Nothing, that sounds fine. It wasn't clear to me that your kick
>> operation left persistent state, and so has a level-triggered effect on hlt.
>>
>
> btw, this persistent state needs to be saved/restored for live
> migration. Best to put it into some MSR.
>
I did not quite get it. Did you mean, add a new MSR to msrs_to_save[],
and may be retain only the kicked/pv_unhalt flag (persistent state) and
get rid of PVLOCK_KICK vcpu->request?
next prev parent reply other threads:[~2012-01-24 18:51 UTC|newest]
Thread overview: 139+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-14 18:25 [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-14 18:25 ` [PATCH RFC V4 1/5] debugfs: Add support to print u32 array in debugfs Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-14 18:25 ` [PATCH RFC V4 2/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-14 18:25 ` Raghavendra K T
2012-01-16 3:24 ` Alexander Graf
2012-01-16 3:24 ` Alexander Graf
2012-01-16 8:43 ` Raghavendra K T
2012-01-16 8:43 ` Raghavendra K T
2012-01-16 9:03 ` Avi Kivity
2012-01-16 9:03 ` Avi Kivity
2012-01-16 9:55 ` Raghavendra K T
2012-01-16 9:55 ` Raghavendra K T
2012-01-14 18:26 ` [PATCH RFC V4 3/5] kvm guest : Added configuration support to enable debug information for KVM Guests Raghavendra K T
2012-01-14 18:26 ` Raghavendra K T
2012-01-14 18:26 ` Raghavendra K T
2012-01-14 18:26 ` [PATCH RFC V4 4/5] kvm : pv-ticketlocks support for linux guests running on KVM hypervisor Raghavendra K T
2012-01-14 18:26 ` Raghavendra K T
2012-01-14 18:26 ` Raghavendra K T
2012-01-16 3:12 ` Alexander Graf
2012-01-16 3:12 ` Alexander Graf
2012-01-16 7:25 ` Raghavendra K T
2012-01-16 7:25 ` Raghavendra K T
2012-01-16 9:05 ` Avi Kivity
2012-01-16 9:05 ` Avi Kivity
2012-01-16 14:13 ` Raghavendra K T
2012-01-16 14:13 ` Raghavendra K T
2012-01-16 14:47 ` Avi Kivity
2012-01-16 14:47 ` Avi Kivity
2012-01-16 23:49 ` Jeremy Fitzhardinge
2012-01-16 23:49 ` Jeremy Fitzhardinge
2012-01-17 11:02 ` Marcelo Tosatti
2012-01-17 11:02 ` Marcelo Tosatti
2012-01-17 11:33 ` Srivatsa Vaddagiri
2012-01-17 11:33 ` Srivatsa Vaddagiri
2012-01-18 1:34 ` Jeremy Fitzhardinge
2012-01-18 1:34 ` Jeremy Fitzhardinge
2012-01-18 13:54 ` Srivatsa Vaddagiri
2012-01-18 13:54 ` Srivatsa Vaddagiri
2012-01-18 21:52 ` Jeremy Fitzhardinge
2012-01-18 21:52 ` Jeremy Fitzhardinge
2012-01-24 14:08 ` Avi Kivity
2012-01-24 14:08 ` Avi Kivity
2012-01-24 18:51 ` Raghavendra K T [this message]
2012-01-24 18:51 ` Raghavendra K T
2012-01-17 18:57 ` Raghavendra K T
2012-01-17 18:57 ` Raghavendra K T
2012-01-24 19:01 ` Raghavendra K T
2012-01-14 18:27 ` [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Raghavendra K T
2012-01-14 18:27 ` Raghavendra K T
2012-01-14 18:27 ` Raghavendra K T
2012-01-14 18:27 ` Raghavendra K T
2012-01-16 3:23 ` Alexander Graf
2012-01-16 3:23 ` Alexander Graf
2012-01-16 3:51 ` Srivatsa Vaddagiri
2012-01-16 3:51 ` Srivatsa Vaddagiri
2012-01-16 4:00 ` Alexander Graf
2012-01-16 4:00 ` Alexander Graf
2012-01-16 8:47 ` Avi Kivity
2012-01-16 8:44 ` Raghavendra K T
2012-01-16 8:44 ` Raghavendra K T
2012-01-16 10:26 ` Alexander Graf
2012-01-16 10:26 ` Alexander Graf
2012-01-16 9:00 ` Avi Kivity
2012-01-16 9:00 ` Avi Kivity
2012-01-16 9:40 ` Srivatsa Vaddagiri
2012-01-16 10:14 ` Avi Kivity
2012-01-16 14:11 ` Srivatsa Vaddagiri
2012-01-17 9:14 ` Gleb Natapov
2012-01-17 9:14 ` Gleb Natapov
2012-01-17 12:26 ` Srivatsa Vaddagiri
2012-01-17 12:26 ` Srivatsa Vaddagiri
2012-01-17 12:51 ` Gleb Natapov
2012-01-17 12:51 ` Gleb Natapov
2012-01-17 13:11 ` Srivatsa Vaddagiri
2012-01-17 13:11 ` Srivatsa Vaddagiri
2012-01-17 13:20 ` Gleb Natapov
2012-01-17 13:20 ` Gleb Natapov
2012-01-17 14:28 ` Srivatsa Vaddagiri
2012-01-17 14:28 ` Srivatsa Vaddagiri
2012-01-17 15:32 ` Gleb Natapov
2012-01-17 15:32 ` Gleb Natapov
2012-01-17 15:53 ` Marcelo Tosatti
2012-01-17 15:53 ` Marcelo Tosatti
2012-01-20 15:09 ` Srivatsa Vaddagiri
2012-01-17 13:13 ` Raghavendra K T
2012-01-17 13:13 ` Raghavendra K T
2012-01-16 3:57 ` [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests Alexander Graf
2012-01-16 3:57 ` Alexander Graf
2012-01-16 6:40 ` Jeremy Fitzhardinge
2012-01-16 6:40 ` Jeremy Fitzhardinge
2012-01-16 8:55 ` Avi Kivity
2012-01-16 8:55 ` Avi Kivity
2012-01-16 23:59 ` Jeremy Fitzhardinge
2012-01-16 23:59 ` Jeremy Fitzhardinge
2012-01-18 10:48 ` Raghavendra K T
2012-01-18 10:48 ` Raghavendra K T
2012-01-16 10:24 ` Alexander Graf
2012-01-16 10:24 ` Alexander Graf
2012-01-17 0:30 ` Jeremy Fitzhardinge
2012-01-17 0:30 ` Jeremy Fitzhardinge
2012-01-18 10:23 ` Raghavendra K T
2012-01-18 10:23 ` Raghavendra K T
2012-01-16 13:43 ` Raghavendra K T
2012-01-16 13:43 ` Raghavendra K T
2012-01-16 13:49 ` Avi Kivity
2012-01-16 13:49 ` Avi Kivity
2012-01-16 18:48 ` Raghavendra K T
2012-01-16 18:48 ` Raghavendra K T
2012-01-16 14:20 ` Srivatsa Vaddagiri
2012-01-16 14:20 ` Srivatsa Vaddagiri
2012-01-16 14:23 ` Alexander Graf
2012-01-16 14:23 ` Alexander Graf
2012-01-16 18:38 ` Raghavendra K T
2012-01-16 18:38 ` Raghavendra K T
2012-01-16 18:42 ` Alexander Graf
2012-01-16 18:42 ` Alexander Graf
2012-01-17 17:27 ` Raghavendra K T
2012-01-17 17:27 ` Raghavendra K T
2012-01-17 17:39 ` Alexander Graf
2012-01-17 17:39 ` Alexander Graf
2012-01-17 18:36 ` Raghavendra K T
2012-01-17 18:36 ` Raghavendra K T
2012-01-17 21:57 ` Dave Hansen
2012-01-17 21:57 ` Dave Hansen
2012-01-18 2:27 ` Raghavendra K T
2012-01-18 2:27 ` Raghavendra K T
2012-01-25 8:55 ` Raghavendra K T
2012-01-25 8:55 ` Raghavendra K T
2012-01-25 16:35 ` Konrad Rzeszutek Wilk
2012-01-25 16:35 ` Konrad Rzeszutek Wilk
2012-01-25 17:45 ` Raghavendra K T
2012-01-25 17:45 ` Raghavendra K T
2012-01-25 19:05 ` Konrad Rzeszutek Wilk
2012-01-25 19:05 ` Konrad Rzeszutek Wilk
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