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Subject[PATCH 27/43] KVM: ia64: SN2 adjust emulated ITC frequency to match RTC frequency
Date
From: Jes Sorensen <jes@sgi.com>

On SN2 do not pass down the real ITC frequency, but rather patch the
values to match the SN2 RTC frequency.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
arch/ia64/kvm/kvm_fw.c | 28 +++++++++++++++++++++++++++-
1 files changed, 27 insertions(+), 1 deletions(-)

diff --git a/arch/ia64/kvm/kvm_fw.c b/arch/ia64/kvm/kvm_fw.c
index a8ae52e..e4b8231 100644
--- a/arch/ia64/kvm/kvm_fw.c
+++ b/arch/ia64/kvm/kvm_fw.c
@@ -21,6 +21,9 @@

#include <linux/kvm_host.h>
#include <linux/smp.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/clksupport.h>
+#include <asm/sn/shub_mmr.h>

#include "vti.h"
#include "misc.h"
@@ -188,12 +191,35 @@ static struct ia64_pal_retval pal_freq_base(struct kvm_vcpu *vcpu)
return result;
}

-static struct ia64_pal_retval pal_freq_ratios(struct kvm_vcpu *vcpu)
+/*
+ * On the SGI SN2, the ITC isn't stable. Emulation backed by the SN2
+ * RTC is used instead. This function patches the ratios from SAL
+ * to match the RTC before providing them to the guest.
+ */
+static void sn2_patch_itc_freq_ratios(struct ia64_pal_retval *result)
{
+ struct pal_freq_ratio *ratio;
+ unsigned long sal_freq, sal_drift, factor;
+
+ result->status = ia64_sal_freq_base(SAL_FREQ_BASE_PLATFORM,
+ &sal_freq, &sal_drift);
+ ratio = (struct pal_freq_ratio *)&result->v2;
+ factor = ((sal_freq * 3) + (sn_rtc_cycles_per_second / 2)) /
+ sn_rtc_cycles_per_second;
+
+ ratio->num = 3;
+ ratio->den = factor;
+}

+static struct ia64_pal_retval pal_freq_ratios(struct kvm_vcpu *vcpu)
+{
struct ia64_pal_retval result;

PAL_CALL(result, PAL_FREQ_RATIOS, 0, 0, 0);
+
+ if (vcpu->kvm->arch.is_sn2)
+ sn2_patch_itc_freq_ratios(&result);
+
return result;
}

--
1.6.0.6


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