[PATCH 3/8] KVM: X86: Pass an additional 'L1' argument to kvm_scale_tsc()

[ilstam@mailbox.org]

From: Ilias Stamatis <ilstam@amazon.com>

Sometimes kvm_scale_tsc() needs to use the current scaling ratio and
other times (like when reading the TSC from user space) it needs to use
L1's scaling ratio. Have the caller specify this by passing an
additional boolean argument.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
---
 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/x86.c              | 21 +++++++++++++--------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 132e820525fb..cdddbf0b1177 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1779,7 +1779,7 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
 void kvm_define_user_return_msr(unsigned index, u32 msr);
 int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask);
 
-u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc);
+u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc, bool l1);
 u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc);
 
 unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7bc5155ac6fd..26a4c0f46f15 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2241,10 +2241,14 @@ static inline u64 __scale_tsc(u64 ratio, u64 tsc)
 	return mul_u64_u64_shr(tsc, ratio, kvm_tsc_scaling_ratio_frac_bits);
 }
 
-u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc)
+/*
+ * If l1 is true the TSC is scaled using L1's scaling ratio, otherwise
+ * the current scaling ratio is used.
+ */
+u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc, bool l1)
 {
 	u64 _tsc = tsc;
-	u64 ratio = vcpu->arch.tsc_scaling_ratio;
+	u64 ratio = l1 ? vcpu->arch.l1_tsc_scaling_ratio : vcpu->arch.tsc_scaling_ratio;
 
 	if (ratio != kvm_default_tsc_scaling_ratio)
 		_tsc = __scale_tsc(ratio, tsc);
@@ -2257,14 +2261,14 @@ static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
 {
 	u64 tsc;
 
-	tsc = kvm_scale_tsc(vcpu, rdtsc());
+	tsc = kvm_scale_tsc(vcpu, rdtsc(), true);
 
 	return target_tsc - tsc;
 }
 
 u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
 {
-	return vcpu->arch.l1_tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
+	return vcpu->arch.l1_tsc_offset + kvm_scale_tsc(vcpu, host_tsc, true);
 }
 EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
 
@@ -2395,9 +2399,9 @@ static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,
 
 static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
 {
-	if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)
+	if (vcpu->arch.l1_tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)
 		WARN_ON(adjustment < 0);
-	adjustment = kvm_scale_tsc(vcpu, (u64) adjustment);
+	adjustment = kvm_scale_tsc(vcpu, (u64) adjustment, true);
 	adjust_tsc_offset_guest(vcpu, adjustment);
 }
 
@@ -2780,7 +2784,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 	/* With all the info we got, fill in the values */
 
 	if (kvm_has_tsc_control)
-		tgt_tsc_khz = kvm_scale_tsc(v, tgt_tsc_khz);
+		tgt_tsc_khz = kvm_scale_tsc(v, tgt_tsc_khz, true);
 
 	if (unlikely(vcpu->hw_tsc_khz != tgt_tsc_khz)) {
 		kvm_get_time_scale(NSEC_PER_SEC, tgt_tsc_khz * 1000LL,
@@ -3474,7 +3478,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		u64 tsc_offset = msr_info->host_initiated ? vcpu->arch.l1_tsc_offset :
 							    vcpu->arch.tsc_offset;
 
-		msr_info->data = kvm_scale_tsc(vcpu, rdtsc()) + tsc_offset;
+		msr_info->data = kvm_scale_tsc(vcpu, rdtsc(),
+					       msr_info->host_initiated) + tsc_offset;
 		break;
 	}
 	case MSR_MTRRcap:
-- 
2.17.1