releases/4.16.17/kvm-x86-lower-the-default-timer-frequency-limit-to-200us.patch

From foo@baz Sun Jun 17 12:07:34 CEST 2018
From: Wanpeng Li <wanpengli@tencent.com>
Date: Sat, 5 May 2018 04:02:32 -0700
Subject: KVM: X86: Lower the default timer frequency limit to 200us

From: Wanpeng Li <wanpengli@tencent.com>

[ Upstream commit 4c27625b7a67eb9006963ed2bcf8e53b259b43af ]

Anthoine reported:
 The period used by Windows change over time but it can be 1
 milliseconds or less. I saw the limit_periodic_timer_frequency
 print so 500 microseconds is sometimes reached.

As suggested by Paolo, lower the default timer frequency limit to a
smaller interval of 200 us (5000 Hz) to leave some headroom. This
is required due to Windows 10 changing the scheduler tick limit
from 1024 Hz to 2048 Hz.

Reported-by: Anthoine Bourgeois <anthoine.bourgeois@blade-group.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Anthoine Bourgeois <anthoine.bourgeois@blade-group.com>
Cc: Darren Kenny <darren.kenny@oracle.com>
Cc: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kvm/x86.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -112,7 +112,7 @@ module_param(ignore_msrs, bool, S_IRUGO
 static bool __read_mostly report_ignored_msrs = true;
 module_param(report_ignored_msrs, bool, S_IRUGO | S_IWUSR);
 
-unsigned int min_timer_period_us = 500;
+unsigned int min_timer_period_us = 200;
 module_param(min_timer_period_us, uint, S_IRUGO | S_IWUSR);
 
 static bool __read_mostly kvmclock_periodic_sync = true;