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

Signed-off-by: Peter Shier <pshier@google.com>
Signed-off-by: Makarand Sonare <makarandsonare@google.com>
Message-Id: <20200526215107.205814-2-makarandsonare@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index d0569db..db22e83 100644 (file)
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -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;

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 12075a9..17c5a03 100644 (file)
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -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;

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 119a2f7..da87bb8 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -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;
@@ -3957,9 +3980,10 @@ 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->vmx_preemption_timer_value =
-                               vmx_get_preemption_timer_value(vcpu);
+           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);
 
        /*
         * In some cases (usually, nested EPT), L2 is allowed to change its
@@ -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))

diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 298ddef..672c28f 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -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 */