[PATCH 1/2] KVM: nVMX: Fix VMX preemption timer migration

[Makarand Sonare <makarandsonare@google.com>]

From: Peter Shier <pshier@google.com>

Add new field to hold preemption timer expiration deadline
appended to struct kvm_vmx_nested_state_data. This is to prevent
the first VM-Enter after migration from incorrectly restarting the timer
with the full timer value instead of partially decayed timer value.
KVM_SET_NESTED_STATE restarts timer using migrated state regardless
of whether L1 sets VM_EXIT_SAVE_VMX_PREEMPTION_TIMER.

Fixes: cf8b84f48a593 ("kvm: nVMX: Prepare for checkpointing L2 state")

Signed-off-by: Peter Shier <pshier@google.com>
Signed-off-by: Makarand Sonare <makarandsonare@google.com>
Change-Id: I6446aba5a547afa667f0ef4620b1b76115bf3753
---
 Documentation/virt/kvm/api.rst        |  4 ++
 arch/x86/include/uapi/asm/kvm.h       |  2 +
 arch/x86/kvm/vmx/nested.c             | 61 ++++++++++++++++++++++++---
 arch/x86/kvm/vmx/vmx.h                |  1 +
 arch/x86/kvm/x86.c                    |  3 +-
 include/uapi/linux/kvm.h              |  1 +
 tools/arch/x86/include/uapi/asm/kvm.h |  2 +
 7 files changed, 67 insertions(+), 7 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index d871dacb984e9..b410815772970 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4326,6 +4326,9 @@ Errors:
   #define KVM_STATE_NESTED_RUN_PENDING		0x00000002
   #define KVM_STATE_NESTED_EVMCS		0x00000004
 
+  /* Available with KVM_CAP_NESTED_STATE_PREEMPTION_TIMER */
+  #define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010
+
   #define KVM_STATE_NESTED_FORMAT_VMX		0
   #define KVM_STATE_NESTED_FORMAT_SVM		1
 
@@ -4346,6 +4349,7 @@ Errors:
   struct kvm_vmx_nested_state_data {
 	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
 	__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+	__u64 preemption_timer_deadline;
   };
 
 This ioctl copies the vcpu's nested virtualization state from the kernel to
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 3f3f780c8c650..20d5832bab215 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -391,6 +391,7 @@ struct kvm_sync_regs {
 #define KVM_STATE_NESTED_RUN_PENDING	0x00000002
 #define KVM_STATE_NESTED_EVMCS		0x00000004
 #define KVM_STATE_NESTED_MTF_PENDING	0x00000008
+#define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010
 
 #define KVM_STATE_NESTED_SMM_GUEST_MODE	0x00000001
 #define KVM_STATE_NESTED_SMM_VMXON	0x00000002
@@ -400,6 +401,7 @@ struct kvm_sync_regs {
 struct kvm_vmx_nested_state_data {
 	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
 	__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+	__u64 preemption_timer_deadline;
 };
 
 struct kvm_vmx_nested_state_hdr {
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 51ebb60e1533a..badb82a39ac04 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2092,9 +2092,9 @@ static enum hrtimer_restart vmx_preemption_timer_fn(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
-static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu)
+static void vmx_start_preemption_timer(struct kvm_vcpu *vcpu,
+					u64 preemption_timeout)
 {
-	u64 preemption_timeout = get_vmcs12(vcpu)->vmx_preemption_timer_value;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
 	/*
@@ -3353,8 +3353,24 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	 * the timer.
 	 */
 	vmx->nested.preemption_timer_expired = false;
-	if (nested_cpu_has_preemption_timer(vmcs12))
-		vmx_start_preemption_timer(vcpu);
+	if (nested_cpu_has_preemption_timer(vmcs12)) {
+		u64 timer_value;
+		u64 l1_tsc_value = kvm_read_l1_tsc(vcpu, rdtsc());
+
+		if (from_vmentry) {
+			timer_value = vmcs12->vmx_preemption_timer_value;
+			vmx->nested.preemption_timer_deadline = timer_value +
+				(l1_tsc_value >> VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE);
+		} else {
+			if ((l1_tsc_value >> VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE) >
+			    vmx->nested.preemption_timer_deadline)
+				timer_value = 0;
+			else
+				timer_value = vmx->nested.preemption_timer_deadline -
+					(l1_tsc_value >> VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE);
+		}
+		vmx_start_preemption_timer(vcpu, timer_value);
+	}
 
 	/*
 	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
@@ -3962,9 +3978,11 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 		vmcs12->guest_activity_state = GUEST_ACTIVITY_ACTIVE;
 
 	if (nested_cpu_has_preemption_timer(vmcs12) &&
-	    vmcs12->vm_exit_controls & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
+	    !vmx->nested.nested_run_pending) {
+		if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
 			vmcs12->vmx_preemption_timer_value =
 				vmx_get_preemption_timer_value(vcpu);
+	}
 
 	/*
 	 * In some cases (usually, nested EPT), L2 is allowed to change its
@@ -5939,6 +5957,13 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
 
 			if (vmx->nested.mtf_pending)
 				kvm_state.flags |= KVM_STATE_NESTED_MTF_PENDING;
+
+			if (nested_cpu_has_preemption_timer(vmcs12)) {
+				kvm_state.flags |=
+					KVM_STATE_NESTED_PREEMPTION_TIMER;
+				kvm_state.size = offsetof(struct kvm_nested_state, data.vmx) +
+						 offsetofend(struct kvm_vmx_nested_state_data, preemption_timer_deadline);
+			}
 		}
 	}
 
@@ -5970,6 +5995,9 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
 
 	BUILD_BUG_ON(sizeof(user_vmx_nested_state->vmcs12) < VMCS12_SIZE);
 	BUILD_BUG_ON(sizeof(user_vmx_nested_state->shadow_vmcs12) < VMCS12_SIZE);
+	BUILD_BUG_ON(sizeof(user_vmx_nested_state->preemption_timer_deadline)
+		    != sizeof(vmx->nested.preemption_timer_deadline));
+
 
 	/*
 	 * Copy over the full allocated size of vmcs12 rather than just the size
@@ -5985,6 +6013,12 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu,
 			return -EFAULT;
 	}
 
+	if (kvm_state.flags & KVM_STATE_NESTED_PREEMPTION_TIMER) {
+		if (put_user(vmx->nested.preemption_timer_deadline,
+			     &user_vmx_nested_state->preemption_timer_deadline))
+			return -EFAULT;
+	}
+
 out:
 	return kvm_state.size;
 }
@@ -6056,7 +6090,8 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 	 */
 	if (is_smm(vcpu) ?
 		(kvm_state->flags &
-		 (KVM_STATE_NESTED_GUEST_MODE | KVM_STATE_NESTED_RUN_PENDING))
+		 (KVM_STATE_NESTED_GUEST_MODE | KVM_STATE_NESTED_RUN_PENDING |
+		  KVM_STATE_NESTED_PREEMPTION_TIMER))
 		: kvm_state->hdr.vmx.smm.flags)
 		return -EINVAL;
 
@@ -6146,6 +6181,20 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 			goto error_guest_mode;
 	}
 
+	if (kvm_state->flags & KVM_STATE_NESTED_PREEMPTION_TIMER) {
+
+		if (kvm_state->size <
+		    offsetof(struct kvm_nested_state, data.vmx) +
+		    offsetofend(struct kvm_vmx_nested_state_data, preemption_timer_deadline))
+			goto error_guest_mode;
+
+		if (get_user(vmx->nested.preemption_timer_deadline,
+			     &user_vmx_nested_state->preemption_timer_deadline)) {
+			ret = -EFAULT;
+			goto error_guest_mode;
+		}
+	}
+
 	if (nested_vmx_check_controls(vcpu, vmcs12) ||
 	    nested_vmx_check_host_state(vcpu, vmcs12) ||
 	    nested_vmx_check_guest_state(vcpu, vmcs12, &ignored))
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 298ddef79d009..db697400755fb 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -169,6 +169,7 @@ struct nested_vmx {
 	u16 posted_intr_nv;
 
 	struct hrtimer preemption_timer;
+	u64 preemption_timer_deadline;
 	bool preemption_timer_expired;
 
 	/* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 471fccf7f8501..ba9e62ffbb4cd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3418,6 +3418,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_MSR_PLATFORM_INFO:
 	case KVM_CAP_EXCEPTION_PAYLOAD:
 	case KVM_CAP_SET_GUEST_DEBUG:
+	case KVM_CAP_NESTED_STATE_PREEMPTION_TIMER:
 		r = 1;
 		break;
 	case KVM_CAP_SYNC_REGS:
@@ -4626,7 +4627,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 
 		if (kvm_state.flags &
 		    ~(KVM_STATE_NESTED_RUN_PENDING | KVM_STATE_NESTED_GUEST_MODE
-		      | KVM_STATE_NESTED_EVMCS))
+		      | KVM_STATE_NESTED_EVMCS | KVM_STATE_NESTED_PREEMPTION_TIMER))
 			break;
 
 		/* nested_run_pending implies guest_mode.  */
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index ac9eba0289d1b..0868dce12a715 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1018,6 +1018,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_S390_PROTECTED 180
 #define KVM_CAP_PPC_SECURE_GUEST 181
 #define KVM_CAP_HALT_POLL 182
+#define KVM_CAP_NESTED_STATE_PREEMPTION_TIMER 183
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
diff --git a/tools/arch/x86/include/uapi/asm/kvm.h b/tools/arch/x86/include/uapi/asm/kvm.h
index 3f3f780c8c650..60701178b9cc1 100644
--- a/tools/arch/x86/include/uapi/asm/kvm.h
+++ b/tools/arch/x86/include/uapi/asm/kvm.h
@@ -391,6 +391,8 @@ struct kvm_sync_regs {
 #define KVM_STATE_NESTED_RUN_PENDING	0x00000002
 #define KVM_STATE_NESTED_EVMCS		0x00000004
 #define KVM_STATE_NESTED_MTF_PENDING	0x00000008
+/* Available with KVM_CAP_NESTED_STATE_PREEMPTION_TIMER */
+#define KVM_STATE_NESTED_PREEMPTION_TIMER	0x00000010
 
 #define KVM_STATE_NESTED_SMM_GUEST_MODE	0x00000001
 #define KVM_STATE_NESTED_SMM_VMXON	0x00000002
-- 
2.26.2.761.g0e0b3e54be-goog