KVM: x86: Replace call-back set_tsc_khz() with a common function

Both VMX and SVM propagate virtual_tsc_khz in the same way, so this
patch removes the call-back set_tsc_khz() and replaces it with a common
function.
Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -853,7 +853,6 @@ struct kvm_x86_ops {
 
 	bool (*has_wbinvd_exit)(void);
 
-	void (*set_tsc_khz)(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale);
 	u64 (*read_tsc_offset)(struct kvm_vcpu *vcpu);
 	void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
 

arch/x86/kvm/svm.c

@@ -957,41 +957,6 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
 	seg->base = 0;
 }
 
-static void svm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
-{
-	u64 ratio;
-	u64 khz;
-
-	/* Guest TSC same frequency as host TSC? */
-	if (!scale) {
-		vcpu->arch.tsc_scaling_ratio = TSC_RATIO_DEFAULT;
-		return;
-	}
-
-	/* TSC scaling supported? */
-	if (!boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {
-		if (user_tsc_khz > tsc_khz) {
-			vcpu->arch.tsc_catchup = 1;
-			vcpu->arch.tsc_always_catchup = 1;
-		} else
-			WARN(1, "user requested TSC rate below hardware speed\n");
-		return;
-	}
-
-	khz = user_tsc_khz;
-
-	/* TSC scaling required  - calculate ratio */
-	ratio = khz << 32;
-	do_div(ratio, tsc_khz);
-
-	if (ratio == 0 || ratio & TSC_RATIO_RSVD) {
-		WARN_ONCE(1, "Invalid TSC ratio - virtual-tsc-khz=%u\n",
-				user_tsc_khz);
-		return;
-	}
-	vcpu->arch.tsc_scaling_ratio = ratio;
-}
-
 static u64 svm_read_tsc_offset(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -4402,7 +4367,6 @@ static struct kvm_x86_ops svm_x86_ops = {
 
 	.has_wbinvd_exit = svm_has_wbinvd_exit,
 
-	.set_tsc_khz = svm_set_tsc_khz,
 	.read_tsc_offset = svm_read_tsc_offset,
 	.write_tsc_offset = svm_write_tsc_offset,
 	.adjust_tsc_offset = svm_adjust_tsc_offset,

arch/x86/kvm/vmx.c

@@ -2382,22 +2382,6 @@ static u64 vmx_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
 	return host_tsc + tsc_offset;
 }
 
-/*
- * Engage any workarounds for mis-matched TSC rates.  Currently limited to
- * software catchup for faster rates on slower CPUs.
- */
-static void vmx_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
-{
-	if (!scale)
-		return;
-
-	if (user_tsc_khz > tsc_khz) {
-		vcpu->arch.tsc_catchup = 1;
-		vcpu->arch.tsc_always_catchup = 1;
-	} else
-		WARN(1, "user requested TSC rate below hardware speed\n");
-}
-
 static u64 vmx_read_tsc_offset(struct kvm_vcpu *vcpu)
 {
 	return vmcs_read64(TSC_OFFSET);
@@ -10826,7 +10810,6 @@ static struct kvm_x86_ops vmx_x86_ops = {
 
 	.has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
 
-	.set_tsc_khz = vmx_set_tsc_khz,
 	.read_tsc_offset = vmx_read_tsc_offset,
 	.write_tsc_offset = vmx_write_tsc_offset,
 	.adjust_tsc_offset = vmx_adjust_tsc_offset,

arch/x86/kvm/x86.c

@@ -1253,7 +1253,43 @@ static u32 adjust_tsc_khz(u32 khz, s32 ppm)
 	return v;
 }
 
-static void kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 this_tsc_khz)
+static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
+{
+	u64 ratio;
+
+	/* Guest TSC same frequency as host TSC? */
+	if (!scale) {
+		vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
+		return 0;
+	}
+
+	/* TSC scaling supported? */
+	if (!kvm_has_tsc_control) {
+		if (user_tsc_khz > tsc_khz) {
+			vcpu->arch.tsc_catchup = 1;
+			vcpu->arch.tsc_always_catchup = 1;
+			return 0;
+		} else {
+			WARN(1, "user requested TSC rate below hardware speed\n");
+			return -1;
+		}
+	}
+
+	/* TSC scaling required  - calculate ratio */
+	ratio = mul_u64_u32_div(1ULL << kvm_tsc_scaling_ratio_frac_bits,
+				user_tsc_khz, tsc_khz);
+
+	if (ratio == 0 || ratio >= kvm_max_tsc_scaling_ratio) {
+		WARN_ONCE(1, "Invalid TSC scaling ratio - virtual-tsc-khz=%u\n",
+			  user_tsc_khz);
+		return -1;
+	}
+
+	vcpu->arch.tsc_scaling_ratio = ratio;
+	return 0;
+}
+
+static int kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 this_tsc_khz)
 {
 	u32 thresh_lo, thresh_hi;
 	int use_scaling = 0;
@@ -1262,7 +1298,7 @@ static void kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 this_tsc_khz)
 	if (this_tsc_khz == 0) {
 		/* set tsc_scaling_ratio to a safe value */
 		vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
-		return;
+		return -1;
 	}
 
 	/* Compute a scale to convert nanoseconds in TSC cycles */
@@ -1283,7 +1319,7 @@ static void kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 this_tsc_khz)
 		pr_debug("kvm: requested TSC rate %u falls outside tolerance [%u,%u]\n", this_tsc_khz, thresh_lo, thresh_hi);
 		use_scaling = 1;
 	}
-	kvm_x86_ops->set_tsc_khz(vcpu, this_tsc_khz, use_scaling);
+	return set_tsc_khz(vcpu, this_tsc_khz, use_scaling);
 }
 
 static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns)
@@ -3353,9 +3389,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (user_tsc_khz == 0)
 			user_tsc_khz = tsc_khz;
 
-		kvm_set_tsc_khz(vcpu, user_tsc_khz);
-
+		if (!kvm_set_tsc_khz(vcpu, user_tsc_khz))
 			r = 0;
+
 		goto out;
 	}
 	case KVM_GET_TSC_KHZ: {

include/linux/math64.h

@@ -214,4 +214,33 @@ static inline u64 mul_u64_u64_shr(u64 a, u64 b, unsigned int shift)
 
 #endif
 
+#ifndef mul_u64_u32_div
+static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor)
+{
+	union {
+		u64 ll;
+		struct {
+#ifdef __BIG_ENDIAN
+			u32 high, low;
+#else
+			u32 low, high;
+#endif
+		} l;
+	} u, rl, rh;
+
+	u.ll = a;
+	rl.ll = (u64)u.l.low * mul;
+	rh.ll = (u64)u.l.high * mul + rl.l.high;
+
+	/* Bits 32-63 of the result will be in rh.l.low. */
+	rl.l.high = do_div(rh.ll, divisor);
+
+	/* Bits 0-31 of the result will be in rl.l.low.	*/
+	do_div(rl.ll, divisor);
+
+	rl.l.high = rh.l.low;
+	return rl.ll;
+}
+#endif /* mul_u64_u32_div */
+
 #endif /* _LINUX_MATH64_H */