From: David Woodhouse <dwmw@amazon.co.uk>
Date: Fri, 26 Apr 2024 17:24:10 +0000 (+0100)
Subject: KVM: x86: Kill cur_tsc_{nsec,offset,write} fields
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=767d5e71e259cd515eae697a97b1af248e332d8d;p=users%2Fdwmw2%2Flinux.git

KVM: x86: Kill cur_tsc_{nsec,offset,write} fields

These pointlessly duplicate the last_tsc_{nsec,offset,write} values.

The only place they were used was where the TSC is stable and a new vCPU
is being synchronized to the previous setting, in which case the 'last_'
value is definitely identical.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
---

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index dbe5a4c506dac..ccc3c8f808db0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1358,9 +1358,6 @@ struct kvm_arch {
 	u32 last_tsc_khz;
 	u64 last_tsc_offset;
 	u64 last_tsc_scaling_ratio;
-	u64 cur_tsc_nsec;
-	u64 cur_tsc_write;
-	u64 cur_tsc_offset;
 	u64 cur_tsc_generation;
 	int nr_vcpus_matched_tsc;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 39b20c60332d8..0584a41b461df 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2703,11 +2703,9 @@ static void __kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 offset, u64 tsc,
 	lockdep_assert_held(&kvm->arch.tsc_write_lock);
 
 	/*
-	 * We also track th most recent recorded KHZ, write and time to
-	 * allow the matching interval to be extended at each write.
+	 * Track the last recorded kHz (and associated scaling ratio for
+	 * calculating the guest TSC), and offset.
 	 */
-	kvm->arch.last_tsc_nsec = ns;
-	kvm->arch.last_tsc_write = tsc;
 	kvm->arch.last_tsc_khz = vcpu->arch.virtual_tsc_khz;
 	kvm->arch.last_tsc_scaling_ratio = vcpu->arch.l1_tsc_scaling_ratio;
 	kvm->arch.last_tsc_offset = offset;
@@ -2726,10 +2724,9 @@ static void __kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 offset, u64 tsc,
 		 *
 		 * These values are tracked in kvm->arch.cur_xxx variables.
 		 */
+		kvm->arch.last_tsc_nsec = ns;
+		kvm->arch.last_tsc_write = tsc;
 		kvm->arch.cur_tsc_generation++;
-		kvm->arch.cur_tsc_nsec = ns;
-		kvm->arch.cur_tsc_write = tsc;
-		kvm->arch.cur_tsc_offset = offset;
 		kvm->arch.nr_vcpus_matched_tsc = 0;
 	} else if (vcpu->arch.this_tsc_generation != kvm->arch.cur_tsc_generation) {
 		kvm->arch.nr_vcpus_matched_tsc++;
@@ -2737,8 +2734,8 @@ static void __kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 offset, u64 tsc,
 
 	/* Keep track of which generation this VCPU has synchronized to */
 	vcpu->arch.this_tsc_generation = kvm->arch.cur_tsc_generation;
-	vcpu->arch.this_tsc_nsec = kvm->arch.cur_tsc_nsec;
-	vcpu->arch.this_tsc_write = kvm->arch.cur_tsc_write;
+	vcpu->arch.this_tsc_nsec = kvm->arch.last_tsc_nsec;
+	vcpu->arch.this_tsc_write = kvm->arch.last_tsc_write;
 
 	kvm_track_tsc_matching(vcpu);
 }
@@ -2815,8 +2812,8 @@ static void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 *user_value)
 		data = kvm->arch.last_tsc_write;
 
 		if (!kvm_check_tsc_unstable()) {
-			offset = kvm->arch.cur_tsc_offset;
-			ns = kvm->arch.cur_tsc_nsec;
+			offset = kvm->arch.last_tsc_offset;
+			ns = kvm->arch.last_tsc_nsec;
 		} else {
 			/*
 			 * ... unless the TSC is unstable and has to be