[PATCH v8 6/8] kvm, mem-hotplug: Reload L1's apic access page on migration when L2 is running.

[Tang Chen <tangchen@cn.fujitsu.com>]

We are handling "L1 and L2 share one apic access page" situation when migrating
apic access page. We should do some handling when migration happens in the
following situations:

   1) when L0 is running: Update L1's vmcs in the next L0->L1 entry and L2's
      vmcs in the next L1->L2 entry.

   2) when L1 is running: Force a L1->L0 exit, update L1's vmcs in the next
      L0->L1 entry and L2's vmcs in the next L1->L2 entry.

   3) when L2 is running: Force a L2->L0 exit, update L2's vmcs in the next
      L0->L2 entry and L1's vmcs in the next L2->L1 exit.

This patch handles 3).

In L0->L2 entry, L2's vmcs will be updated in prepare_vmcs02() called by
nested_vm_run(). So we need to do nothing.

In L2->L1 exit, this patch requests apic access page reload in L2->L1 vmexit.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/vmx.c              | 6 ++++++
 arch/x86/kvm/x86.c              | 3 ++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 582cd0f..66480fd 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1046,6 +1046,7 @@ int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);
 int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu);
 int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
 void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
+void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu);
 
 void kvm_define_shared_msr(unsigned index, u32 msr);
 void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1411bab..40bb9fc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8826,6 +8826,12 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
 	}
 
 	/*
+	 * We are now running in L2, mmu_notifier will force to reload the
+	 * page's hpa for L2 vmcs. Need to reload it for L1 before entering L1.
+	 */
+	kvm_vcpu_reload_apic_access_page(vcpu);
+
+	/*
 	 * Exiting from L2 to L1, we're now back to L1 which thinks it just
 	 * finished a VMLAUNCH or VMRESUME instruction, so we need to set the
 	 * success or failure flag accordingly.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1f0c99a..c064ca6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5989,7 +5989,7 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
 	kvm_apic_update_tmr(vcpu, tmr);
 }
 
-static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
+void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
 {
 	/*
 	 * If platform doesn't have 2nd exec virtualize apic access affinity,
@@ -6009,6 +6009,7 @@ static void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
 	kvm_x86_ops->set_apic_access_page_addr(vcpu,
 			page_to_phys(vcpu->kvm->arch.apic_access_page));
 }
+EXPORT_SYMBOL_GPL(kvm_vcpu_reload_apic_access_page);
 
 /*
  * Returns 1 to let __vcpu_run() continue the guest execution loop without
-- 
1.8.3.1