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SubjectRE: [PATCH] KVM: tsc deadline timer works only when hrtimer high resolution configured
Date
Avi Kivity wrote:
> On 09/09/2012 05:54 PM, Liu, Jinsong wrote:
>>>
>>> hrtimers is an intrusive feature, I don't think we should
>>> force-enable it. Please change it to a depends on.
>>
>> Hmm, if it changed as
>> config KVM
>> depends on HIGH_RES_TIMERS
>> The item 'Kernel-based Virtual Machine (KVM) support (NEW)' even
>> didn't appear to user when make menuconfig (when HIGH_RES_TIMERS
>> disable)
>>
>> Is it good? I just have a little concern here:)
>
> It's not good, but that's what we have.
>
> It's okay to force-enable low-impact features (like preempt notifies).
>
> hrimers, on the other hand, change kernel behaviour quite deeply.
>
> Maybe over time someone will fix the config tools to unhide features
> that can be enabled by turning on a dependency.

OK, updated as attached.

Thanks,
Jinsong

===============
From e6c2a80d3111cc6fb992d78b242619706d99bc6b Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong.liu@intel.com>
Date: Mon, 10 Sep 2012 06:55:39 +0800
Subject: [PATCH] KVM: KVM enable depends on HIGH_RES_TIMERS

KVM lapic timer and tsc deadline timer based on hrtimer,
setting a leftmost node to rb tree and then do hrtimer reprogram.
If hrtimer not configured as high resolution, hrtimer_enqueue_reprogram
do nothing and then make kvm lapic timer and tsc deadline timer fail.

Signed-off-by: Liu, Jinsong <jinsong.liu@intel.com>
---
arch/x86/kvm/Kconfig | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index a28f338..65657ec 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -20,6 +20,7 @@ if VIRTUALIZATION
config KVM
tristate "Kernel-based Virtual Machine (KVM) support"
depends on HAVE_KVM
+ depends on HIGH_RES_TIMERS
# for device assignment:
depends on PCI
# for TASKSTATS/TASK_DELAY_ACCT:
--
1.7.1[unhandled content-type:application/octet-stream]
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