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Date: Mon, 28 Sep 2015 13:38:02 +0800
From: Haozhong Zhang <haozhong.zhang@...el.com>
To: kvm@...r.kernel.org
Cc: Gleb Natapov <gleb@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
Joerg Roedel <joro@...tes.org>,
Wanpeng Li <wanpeng.li@...ux.intel.com>,
Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
Mihai Donțu <mdontu@...defender.com>,
Andy Lutomirski <luto@...nel.org>,
Kai Huang <kai.huang@...ux.intel.com>,
linux-kernel@...r.kernel.org,
Haozhong Zhang <haozhong.zhang@...el.com>
Subject: [PATCH 03/12] KVM: x86: Add a common TSC scaling function
VMX and SVM calculate the TSC scaling ratio in a similar logic, so this
patch generalizes it to a common TSC scaling function.
Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
---
arch/x86/kvm/svm.c | 48 +++------------------------------
arch/x86/kvm/x86.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/kvm_host.h | 4 ++-
3 files changed, 77 insertions(+), 45 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index a3186e2..1a333bd 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -209,7 +209,6 @@ static int nested_svm_intercept(struct vcpu_svm *svm);
static int nested_svm_vmexit(struct vcpu_svm *svm);
static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
bool has_error_code, u32 error_code);
-static u64 __scale_tsc(u64 ratio, u64 tsc);
enum {
VMCB_INTERCEPTS, /* Intercept vectors, TSC offset,
@@ -947,21 +946,7 @@ static __init int svm_hardware_setup(void)
kvm_enable_efer_bits(EFER_FFXSR);
if (boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {
- u64 max;
-
kvm_has_tsc_control = true;
-
- /*
- * Make sure the user can only configure tsc_khz values that
- * fit into a signed integer.
- * A min value is not calculated needed because it will always
- * be 1 on all machines and a value of 0 is used to disable
- * tsc-scaling for the vcpu.
- */
- max = min(0x7fffffffULL, __scale_tsc(tsc_khz, TSC_RATIO_MAX));
-
- kvm_max_guest_tsc_khz = max;
-
kvm_max_tsc_scaling_ratio = TSC_RATIO_MAX;
kvm_tsc_scaling_ratio_frac_bits = 32;
kvm_tsc_scaling_ratio_rsvd = TSC_RATIO_RSVD;
@@ -1030,31 +1015,6 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
seg->base = 0;
}
-static u64 __scale_tsc(u64 ratio, u64 tsc)
-{
- u64 mult, frac, _tsc;
-
- mult = ratio >> 32;
- frac = ratio & ((1ULL << 32) - 1);
-
- _tsc = tsc;
- _tsc *= mult;
- _tsc += (tsc >> 32) * frac;
- _tsc += ((tsc & ((1ULL << 32) - 1)) * frac) >> 32;
-
- return _tsc;
-}
-
-static u64 svm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
-{
- u64 _tsc = tsc;
-
- if (vcpu->arch.tsc_scaling_ratio != TSC_RATIO_DEFAULT)
- _tsc = __scale_tsc(vcpu->arch.tsc_scaling_ratio, tsc);
-
- return _tsc;
-}
-
static void svm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
{
u64 ratio;
@@ -1123,7 +1083,7 @@ static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho
if (host) {
if (vcpu->arch.tsc_scaling_ratio != TSC_RATIO_DEFAULT)
WARN_ON(adjustment < 0);
- adjustment = svm_scale_tsc(vcpu, (u64)adjustment);
+ adjustment = kvm_scale_tsc(vcpu, (u64)adjustment);
}
svm->vmcb->control.tsc_offset += adjustment;
@@ -1141,7 +1101,7 @@ static u64 svm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
{
u64 tsc;
- tsc = svm_scale_tsc(vcpu, rdtsc());
+ tsc = kvm_scale_tsc(vcpu, rdtsc());
return target_tsc - tsc;
}
@@ -3166,7 +3126,7 @@ static u64 svm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
{
struct vmcb *vmcb = get_host_vmcb(to_svm(vcpu));
return vmcb->control.tsc_offset +
- svm_scale_tsc(vcpu, host_tsc);
+ kvm_scale_tsc(vcpu, host_tsc);
}
static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
@@ -3176,7 +3136,7 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
switch (msr_info->index) {
case MSR_IA32_TSC: {
msr_info->data = svm->vmcb->control.tsc_offset +
- svm_scale_tsc(vcpu, rdtsc());
+ kvm_scale_tsc(vcpu, rdtsc());
break;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4a521b4..920c302 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1321,6 +1321,64 @@ static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset)
vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset;
}
+/*
+ * Multiply tsc by a fixed point number represented by ratio.
+ *
+ * The most significant 64-N bits (mult) of ratio represent the
+ * integral part of the fixed point number; the remaining N bits
+ * (frac) represent the fractional part, ie. ratio represents a fixed
+ * point number (mult + frac * 2^(-N)).
+ *
+ * N.B: we always assume not all 64 bits of ratio are used for the
+ * fractional part and the ratio has at least 1 bit for the fractional
+ * part, i.e. 0 < N < 64.
+ *
+ * N equals to kvm_tsc_scaling_ratio_frac_bits.
+ */
+static u64 __scale_tsc(u64 ratio, u64 tsc)
+{
+ u64 mult, frac, mask, _tsc;
+ int width, nr;
+
+ BUG_ON(kvm_tsc_scaling_ratio_frac_bits >= 64 ||
+ kvm_tsc_scaling_ratio_frac_bits == 0);
+
+ mult = ratio >> kvm_tsc_scaling_ratio_frac_bits;
+ mask = (1ULL << kvm_tsc_scaling_ratio_frac_bits) - 1;
+ frac = ratio & mask;
+
+ width = 64 - kvm_tsc_scaling_ratio_frac_bits;
+ mask = (1ULL << width) - 1;
+ nr = kvm_tsc_scaling_ratio_frac_bits;
+
+ _tsc = tsc;
+ _tsc *= mult;
+ _tsc += (tsc >> kvm_tsc_scaling_ratio_frac_bits) * frac;
+
+ while (nr >= width) {
+ _tsc += (((tsc >> (nr - width)) & mask) * frac) >> (64 - nr);
+ nr -= width;
+ }
+
+ if (nr > 0)
+ _tsc += ((tsc & ((1ULL << nr) - 1)) * frac) >>
+ kvm_tsc_scaling_ratio_frac_bits;
+
+ return _tsc;
+}
+
+u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
+{
+ u64 _tsc = tsc;
+ u64 ratio = vcpu->arch.tsc_scaling_ratio;
+
+ if (ratio != kvm_default_tsc_scaling_ratio)
+ _tsc = __scale_tsc(ratio, tsc);
+
+ return _tsc;
+}
+EXPORT_SYMBOL_GPL(kvm_scale_tsc);
+
void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
{
struct kvm *kvm = vcpu->kvm;
@@ -7290,6 +7348,18 @@ int kvm_arch_hardware_setup(void)
if (r != 0)
return r;
+ /*
+ * Make sure the user can only configure tsc_khz values that
+ * fit into a signed integer.
+ * A min value is not calculated needed because it will always
+ * be 1 on all machines.
+ */
+ if (kvm_has_tsc_control) {
+ u64 max = min(0x7fffffffULL,
+ __scale_tsc(kvm_max_tsc_scaling_ratio, tsc_khz));
+ kvm_max_guest_tsc_khz = max;
+ }
+
kvm_init_msr_list();
return 0;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1bef9e2..3c43e3e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1144,5 +1144,7 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
{
}
#endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
-#endif
+u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc);
+
+#endif
--
2.4.8
--
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