Commit 850448f3 authored by Peter Shier's avatar Peter Shier Committed by Paolo Bonzini
Browse files

KVM: nVMX: Fix VMX preemption timer migration 



Add new field to hold preemption timer expiration deadline
appended to struct kvm_vmx_nested_state_hdr. 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: cf8b84f4 ("kvm: nVMX: Prepare for checkpointing L2 state")

Signed-off-by: default avatarPeter Shier <pshier@google.com>
Signed-off-by: default avatarMakarand Sonare <makarandsonare@google.com>
Message-Id: <20200526215107.205814-2-makarandsonare@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f7d31e65

Documentation/virt/kvm/api.rst

+4 −0
Original line number Diff line number Diff line
@@ -4334,9 +4334,13 @@ Errors: 
  #define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE	0x00000001

  #define KVM_STATE_NESTED_VMX_SMM_VMXON	0x00000002



#define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE 0x00000001



  struct kvm_vmx_nested_state_hdr {

	__u32 flags;

	__u64 vmxon_pa;

	__u64 vmcs12_pa;

	__u64 preemption_timer_deadline;



	struct {

		__u16 flags;

arch/x86/include/uapi/asm/kvm.h

+3 −0
Original line number Diff line number Diff line
@@ -400,6 +400,7 @@ struct kvm_sync_regs { 


#define KVM_STATE_NESTED_SVM_VMCB_SIZE	0x1000



#define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE	0x00000001



struct kvm_vmx_nested_state_data {

	__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
@@ -407,8 +408,10 @@ struct kvm_vmx_nested_state_data { 
};



struct kvm_vmx_nested_state_hdr {

	__u32 flags;

	__u64 vmxon_pa;

	__u64 vmcs12_pa;

	__u64 preemption_timer_deadline;



	struct {

		__u16 flags;

arch/x86/kvm/vmx/nested.c

+47 −8
Original line number Diff line number Diff line
@@ -2087,9 +2087,29 @@ 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 u64 vmx_calc_preemption_timer_value(struct kvm_vcpu *vcpu)

{

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);

	u64 timer_value = 0;



	u64 l1_scaled_tsc = kvm_read_l1_tsc(vcpu, rdtsc()) >>

			    VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE;



	if (!vmx->nested.has_preemption_timer_deadline) {

		timer_value = vmcs12->vmx_preemption_timer_value;

		vmx->nested.preemption_timer_deadline = timer_value +

							l1_scaled_tsc;

		vmx->nested.has_preemption_timer_deadline = true;

	} else if (l1_scaled_tsc < vmx->nested.preemption_timer_deadline)

		timer_value = vmx->nested.preemption_timer_deadline -

			      l1_scaled_tsc;

	return timer_value;

}



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);



	/*
@@ -3348,8 +3368,10 @@ 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 = vmx_calc_preemption_timer_value(vcpu);

		vmx_start_preemption_timer(vcpu, timer_value);

	}



	/*

	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
@@ -3457,6 +3479,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) 
	 * the nested entry.

	 */

	vmx->nested.nested_run_pending = 1;

	vmx->nested.has_preemption_timer_deadline = false;

	status = nested_vmx_enter_non_root_mode(vcpu, true);

	if (unlikely(status != NVMX_VMENTRY_SUCCESS))

		goto vmentry_failed;
@@ -3957,7 +3980,8 @@ 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)

	    vmcs12->vm_exit_controls & VM_EXIT_SAVE_VMX_PREEMPTION_TIMER &&

	    !vmx->nested.nested_run_pending)

		vmcs12->vmx_preemption_timer_value =

			vmx_get_preemption_timer_value(vcpu);
@@ -5891,8 +5915,10 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu, 
		.flags = 0,

		.format = KVM_STATE_NESTED_FORMAT_VMX,

		.size = sizeof(kvm_state),

		.hdr.vmx.flags = 0,

		.hdr.vmx.vmxon_pa = -1ull,

		.hdr.vmx.vmcs12_pa = -1ull,

		.hdr.vmx.preemption_timer_deadline = 0,

	};

	struct kvm_vmx_nested_state_data __user *user_vmx_nested_state =

		&user_kvm_nested_state->data.vmx[0];
@@ -5934,6 +5960,14 @@ 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) &&

			    vmx->nested.has_preemption_timer_deadline) {

				kvm_state.hdr.vmx.flags |=

					KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE;

				kvm_state.hdr.vmx.preemption_timer_deadline =

					vmx->nested.preemption_timer_deadline;

			}

		}

	}
@@ -5979,7 +6013,6 @@ static int vmx_get_nested_state(struct kvm_vcpu *vcpu, 
				 get_shadow_vmcs12(vcpu), VMCS12_SIZE))

			return -EFAULT;

	}



out:

	return kvm_state.size;

}
@@ -6141,6 +6174,12 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu, 
			goto error_guest_mode;

	}



	if (kvm_state->hdr.vmx.flags & KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE) {

		vmx->nested.has_preemption_timer_deadline = true;

		vmx->nested.preemption_timer_deadline =

			kvm_state->hdr.vmx.preemption_timer_deadline;

	}



	if (nested_vmx_check_controls(vcpu, vmcs12) ||

	    nested_vmx_check_host_state(vcpu, vmcs12) ||

	    nested_vmx_check_guest_state(vcpu, vmcs12, &ignored))

arch/x86/kvm/vmx/vmx.h

+2 −0
Original line number Diff line number Diff line
@@ -169,6 +169,8 @@ struct nested_vmx { 
	u16 posted_intr_nv;



	struct hrtimer preemption_timer;

	u64 preemption_timer_deadline;

	bool has_preemption_timer_deadline;

	bool preemption_timer_expired;



	/* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */

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