RE: [PATCH] KVM: tsc deadline timer works only when hrtimer high resolution configured

[Liu, Jinsong]

Avi Kivity wrote:
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 148ed66..0e64997 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -2210,7 +2210,11 @@ int kvm_dev_ioctl_check_extension(long ext) 
>>              r = kvm_has_tsc_control; break;
>>      case KVM_CAP_TSC_DEADLINE_TIMER:
>> +#ifdef CONFIG_HIGH_RES_TIMERS
>>              r = boot_cpu_has(X86_FEATURE_TSC_DEADLINE_TIMER); +#else
>> +            r = 0;
>> +#endif
>>              break;
> 
> I prefer a patch making kvm for x86 depend on hrtimers.  kvm already
> provides a high resolution timer to the guest in the local apic,
> backing it with the jiffies event source will likely cause some
> guests to malfunction.

Yep, I did a draft test for kvm lapic timer, it also worked fail when 
CONFIG_HIGH_RES_TIMERS disabled.

Attached is the udpated patch.

Thanks,
Jinsong

====================
>From 64d0458ec50a7d6917adf1e9735ba6e6ae6024ad Mon Sep 17 00:00:00 2001
From: Liu, Jinsong <jinsong....@intel.com>
Date: Sat, 8 Sep 2012 03:32:31 +0800
Subject: [PATCH] KVM: select HIGH_RES_TIMERS when KVM enabled

This is for 2 reasons:
1. it's pointless for kvm lapic timer and tsc deadline timer
when kernel hrtimer not configured as high resolution, since
that would be not accurate based on wheel;
2. 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....@intel.com>
---
 arch/x86/kvm/Kconfig |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index a28f338..5f861ca 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -24,6 +24,8 @@ config KVM
        depends on PCI
        # for TASKSTATS/TASK_DELAY_ACCT:
        depends on NET
+       # for HIGH_RES_TIMERS
+       depends on !ARCH_USES_GETTIMEOFFSET
        select PREEMPT_NOTIFIERS
        select MMU_NOTIFIER
        select ANON_INODES
@@ -37,6 +39,8 @@ config KVM
        select TASK_DELAY_ACCT
        select PERF_EVENTS
        select HAVE_KVM_MSI
+       select GENERIC_CLOCKEVENTS
+       select HIGH_RES_TIMERS
        ---help---
          Support hosting fully virtualized guest machines using hardware
          virtualization extensions.  You will need a fairly recent
-- 
1.7.1

0001-KVM-select-HIGH_RES_TIMERS-when-KVM-enabled.patch
Description: 0001-KVM-select-HIGH_RES_TIMERS-when-KVM-enabled.patch