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authorZachary Amsden <zamsden@gmail.com>2012-02-03 15:43:50 -0200
committerAvi Kivity <avi@redhat.com>2012-03-08 14:09:35 +0200
commitcc578287e3224d0da196cc1d226bdae6b068faa7 (patch)
treec4352ebbd4d35de296622a8be99d76a1a6a48793 /arch/x86/kvm/lapic.c
parenta59cb29e4d81e025192550c2703f305637f016f6 (diff)
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op-kernel-dev-cc578287e3224d0da196cc1d226bdae6b068faa7.tar.gz
KVM: Infrastructure for software and hardware based TSC rate scaling
This requires some restructuring; rather than use 'virtual_tsc_khz' to indicate whether hardware rate scaling is in effect, we consider each VCPU to always have a virtual TSC rate. Instead, there is new logic above the vendor-specific hardware scaling that decides whether it is even necessary to use and updates all rate variables used by common code. This means we can simply query the virtual rate at any point, which is needed for software rate scaling. There is also now a threshold added to the TSC rate scaling; minor differences and variations of measured TSC rate can accidentally provoke rate scaling to be used when it is not needed. Instead, we have a tolerance variable called tsc_tolerance_ppm, which is the maximum variation from user requested rate at which scaling will be used. The default is 250ppm, which is the half the threshold for NTP adjustment, allowing for some hardware variation. In the event that hardware rate scaling is not available, we can kludge a bit by forcing TSC catchup to turn on when a faster than hardware speed has been requested, but there is nothing available yet for the reverse case; this requires a trap and emulate software implementation for RDTSC, which is still forthcoming. [avi: fix 64-bit division on i386] Signed-off-by: Zachary Amsden <zamsden@gmail.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm/lapic.c')
-rw-r--r--arch/x86/kvm/lapic.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 3ee1d83..72975f7 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -731,7 +731,7 @@ static void start_apic_timer(struct kvm_lapic *apic)
u64 guest_tsc, tscdeadline = apic->lapic_timer.tscdeadline;
u64 ns = 0;
struct kvm_vcpu *vcpu = apic->vcpu;
- unsigned long this_tsc_khz = vcpu_tsc_khz(vcpu);
+ unsigned long this_tsc_khz = vcpu->arch.virtual_tsc_khz;
unsigned long flags;
if (unlikely(!tscdeadline || !this_tsc_khz))
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