linux-kernel - [PATCH v2 02/10] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu

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Message-ID: <20210512150945.4591-3-ilstam@amazon.com>
Date:   Wed, 12 May 2021 16:09:37 +0100
From:   Ilias Stamatis <ilstam@...zon.com>
To:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <pbonzini@...hat.com>
CC:     <mlevitsk@...hat.com>, <seanjc@...gle.com>, <vkuznets@...hat.com>,
        <wanpengli@...cent.com>, <jmattson@...gle.com>, <joro@...tes.org>,
        <zamsden@...il.com>, <mtosatti@...hat.com>, <dwmw@...zon.co.uk>,
        <ilstam@...zon.com>
Subject: [PATCH v2 02/10] KVM: X86: Store L1's TSC scaling ratio in 'struct kvm_vcpu_arch'

Store L1's scaling ratio in that struct like we already do for L1's TSC
offset. This allows for easy save/restore when we enter and then exit
the nested guest.

Signed-off-by: Ilias Stamatis <ilstam@...zon.com>
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 5 +++--
 arch/x86/kvm/x86.c              | 6 ++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 55efbacfc244..7dfc609eacd6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -707,7 +707,7 @@ struct kvm_vcpu_arch {
 	} st;
 
 	u64 l1_tsc_offset;
-	u64 tsc_offset;
+	u64 tsc_offset; /* current tsc offset */
 	u64 last_guest_tsc;
 	u64 last_host_tsc;
 	u64 tsc_offset_adjustment;
@@ -721,7 +721,8 @@ struct kvm_vcpu_arch {
 	u32 virtual_tsc_khz;
 	s64 ia32_tsc_adjust_msr;
 	u64 msr_ia32_power_ctl;
-	u64 tsc_scaling_ratio;
+	u64 l1_tsc_scaling_ratio;
+	u64 tsc_scaling_ratio; /* current scaling ratio */
 
 	atomic_t nmi_queued;  /* unprocessed asynchronous NMIs */
 	unsigned nmi_pending; /* NMI queued after currently running handler */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9b6bca616929..07cf5d7ece38 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2185,6 +2185,7 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
 
 	/* Guest TSC same frequency as host TSC? */
 	if (!scale) {
+		vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
 		vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
 		return 0;
 	}
@@ -2211,7 +2212,7 @@ static int set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz, bool scale)
 		return -1;
 	}
 
-	vcpu->arch.tsc_scaling_ratio = ratio;
+	vcpu->arch.l1_tsc_scaling_ratio = vcpu->arch.tsc_scaling_ratio = ratio;
 	return 0;
 }
 
@@ -2223,6 +2224,7 @@ static int kvm_set_tsc_khz(struct kvm_vcpu *vcpu, u32 user_tsc_khz)
 	/* tsc_khz can be zero if TSC calibration fails */
 	if (user_tsc_khz == 0) {
 		/* set tsc_scaling_ratio to a safe value */
+		vcpu->arch.l1_tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
 		vcpu->arch.tsc_scaling_ratio = kvm_default_tsc_scaling_ratio;
 		return -1;
 	}
@@ -2459,7 +2461,7 @@ 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);
 	adjust_tsc_offset_guest(vcpu, adjustment);
-- 
2.17.1