KVM: ia64: SN2 adjust emulated ITC frequency to match RTC frequency
Jes Sorensen [Wed, 25 Feb 2009 16:38:54 +0000 (10:38 -0600)]
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

index a8ae52e..e4b8231 100644 (file)
@@ -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;
 }