This patch contains the following two changes:
1. Fix the bug in nested preemption timer support. If vmexit L2->L0
with some reasons not emulated by L1, preemption timer value should
be save in such exits.
2. Add support of "Save VMX-preemption timer value" VM-Exit controls
to nVMX.

With this patch, nested VMX preemption timer features are fully
supported.

Signed-off-by: Arthur Chunqi Li <yzt...@gmail.com>
---
 arch/x86/kvm/vmx.c |   30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 57b4e12..9579409 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2204,7 +2204,8 @@ static __init void nested_vmx_setup_ctls_msrs(void)
 #ifdef CONFIG_X86_64
                VM_EXIT_HOST_ADDR_SPACE_SIZE |
 #endif
-               VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT;
+               VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT |
+               VM_EXIT_SAVE_VMX_PREEMPTION_TIMER;
        nested_vmx_exit_ctls_high |= (VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
                                      VM_EXIT_LOAD_IA32_EFER);
 
@@ -7578,9 +7579,14 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct 
vmcs12 *vmcs12)
                (vmcs_config.pin_based_exec_ctrl |
                 vmcs12->pin_based_vm_exec_control));
 
-       if (vmcs12->pin_based_vm_exec_control & PIN_BASED_VMX_PREEMPTION_TIMER)
-               vmcs_write32(VMX_PREEMPTION_TIMER_VALUE,
-                            vmcs12->vmx_preemption_timer_value);
+       if (vmcs12->pin_based_vm_exec_control & PIN_BASED_VMX_PREEMPTION_TIMER) 
{
+               if (vmcs12->vm_exit_controls & 
VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)
+                       vmcs12->vmx_preemption_timer_value =
+                               vmcs_read32(VMX_PREEMPTION_TIMER_VALUE);
+               else
+                       vmcs_write32(VMX_PREEMPTION_TIMER_VALUE,
+                                       vmcs12->vmx_preemption_timer_value);
+       }
 
        /*
         * Whether page-faults are trapped is determined by a combination of
@@ -7690,7 +7696,11 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct 
vmcs12 *vmcs12)
         * we should use its exit controls. Note that VM_EXIT_LOAD_IA32_EFER
         * bits are further modified by vmx_set_efer() below.
         */
-       vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl);
+       if (vmcs12->pin_based_vm_exec_control & PIN_BASED_VMX_PREEMPTION_TIMER)
+               vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl |
+                               VM_EXIT_SAVE_VMX_PREEMPTION_TIMER);
+       else
+               vmcs_write32(VM_EXIT_CONTROLS, vmcs_config.vmexit_ctrl);
 
        /* vmcs12's VM_ENTRY_LOAD_IA32_EFER and VM_ENTRY_IA32E_MODE are
         * emulated by vmx_set_efer(), below.
@@ -7912,6 +7922,16 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool 
launch)
        }
 
        /*
+        * If L2 support PIN_BASED_VMX_PREEMPTION_TIMER, L0 must support
+        * VM_EXIT_SAVE_VMX_PREEMPTION_TIMER.
+        */
+       if ((vmcs12->pin_based_vm_exec_control & 
PIN_BASED_VMX_PREEMPTION_TIMER) &&
+                       !(nested_vmx_exit_ctls_high & 
VM_EXIT_SAVE_VMX_PREEMPTION_TIMER)) {
+               nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
+               return 1;
+       }
+
+       /*
         * We're finally done with prerequisite checking, and can start with
         * the nested entry.
         */
-- 
1.7.9.5

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