KVM: X86: Introduce more exit_fastpath_completion enum values

Adds a fastpath_t typedef since enum lines are a bit long, and replace
EXIT_FASTPATH_SKIP_EMUL_INS with two new exit_fastpath_completion enum values.

- EXIT_FASTPATH_EXIT_HANDLED  kvm will still go through it's full run loop,
                              but it would skip invoking the exit handler.

- EXIT_FASTPATH_REENTER_GUEST complete fastpath, guest can be re-entered
                              without invoking the exit handler or going
                              back to vcpu_run

Tested-by: Haiwei Li <lihaiwei@tencent.com>
Cc: Haiwei Li <lihaiwei@tencent.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1588055009-12677-4-git-send-email-wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Wanpeng Li

arch/x86/include/asm/kvm_host.h

@@ -182,8 +182,10 @@ enum {
 
 enum exit_fastpath_completion {
 	EXIT_FASTPATH_NONE,
-	EXIT_FASTPATH_SKIP_EMUL_INS,
+	EXIT_FASTPATH_REENTER_GUEST,
+	EXIT_FASTPATH_EXIT_HANDLED,
 };
+typedef enum exit_fastpath_completion fastpath_t;
 
 struct x86_emulate_ctxt;
 struct x86_exception;

arch/x86/kvm/svm/svm.c

@@ -2893,8 +2893,7 @@ static void svm_get_exit_info(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2)
 	*info2 = control->exit_info_2;
 }
 
-static int handle_exit(struct kvm_vcpu *vcpu,
-	enum exit_fastpath_completion exit_fastpath)
+static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct kvm_run *kvm_run = vcpu->run;
@@ -2952,10 +2951,10 @@ static int handle_exit(struct kvm_vcpu *vcpu,
 		       __func__, svm->vmcb->control.exit_int_info,
 		       exit_code);
 
-	if (exit_fastpath == EXIT_FASTPATH_SKIP_EMUL_INS) {
-		kvm_skip_emulated_instruction(vcpu);
+	if (exit_fastpath != EXIT_FASTPATH_NONE)
 		return 1;
-	} else if (exit_code >= ARRAY_SIZE(svm_exit_handlers)
+
+	if (exit_code >= ARRAY_SIZE(svm_exit_handlers)
 	    || !svm_exit_handlers[exit_code]) {
 		vcpu_unimpl(vcpu, "svm: unexpected exit reason 0x%x\n", exit_code);
 		dump_vmcb(vcpu);
@@ -3324,7 +3323,7 @@ static void svm_cancel_injection(struct kvm_vcpu *vcpu)
 	svm_complete_interrupts(svm);
 }
 
-static enum exit_fastpath_completion svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
+static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 {
 	if (!is_guest_mode(vcpu) &&
 	    to_svm(vcpu)->vmcb->control.exit_code == SVM_EXIT_MSR &&
@@ -3336,9 +3335,9 @@ static enum exit_fastpath_completion svm_exit_handlers_fastpath(struct kvm_vcpu
 
 void __svm_vcpu_run(unsigned long vmcb_pa, unsigned long *regs);
 
-static enum exit_fastpath_completion svm_vcpu_run(struct kvm_vcpu *vcpu)
+static fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
 {
-	enum exit_fastpath_completion exit_fastpath;
+	fastpath_t exit_fastpath;
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];

arch/x86/kvm/vmx/vmx.c

@@ -5926,8 +5926,7 @@ void dump_vmcs(void)
  * The guest has exited.  See if we can fix it or if we need userspace
  * assistance.
  */
-static int vmx_handle_exit(struct kvm_vcpu *vcpu,
-	enum exit_fastpath_completion exit_fastpath)
+static int vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	u32 exit_reason = vmx->exit_reason;
@@ -6034,10 +6033,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
 		}
 	}
 
-	if (exit_fastpath == EXIT_FASTPATH_SKIP_EMUL_INS) {
-		kvm_skip_emulated_instruction(vcpu);
+	if (exit_fastpath != EXIT_FASTPATH_NONE)
 		return 1;
-	}
 
 	if (exit_reason >= kvm_vmx_max_exit_handlers)
 		goto unexpected_vmexit;
@@ -6628,7 +6625,7 @@ void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
 	}
 }
 
-static enum exit_fastpath_completion vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
+static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 {
 	switch (to_vmx(vcpu)->exit_reason) {
 	case EXIT_REASON_MSR_WRITE:
@@ -6640,12 +6637,13 @@ static enum exit_fastpath_completion vmx_exit_handlers_fastpath(struct kvm_vcpu
 
 bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
 
-static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
+static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 {
-	enum exit_fastpath_completion exit_fastpath;
+	fastpath_t exit_fastpath;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long cr3, cr4;
 
+reenter_guest:
 	/* Record the guest's net vcpu time for enforced NMI injections. */
 	if (unlikely(!enable_vnmi &&
 		     vmx->loaded_vmcs->soft_vnmi_blocked))
@@ -6807,6 +6805,18 @@ static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		return EXIT_FASTPATH_NONE;
 
 	exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
+	if (exit_fastpath == EXIT_FASTPATH_REENTER_GUEST) {
+		if (!kvm_vcpu_exit_request(vcpu)) {
+			/*
+			 * FIXME: this goto should be a loop in vcpu_enter_guest,
+			 * but it would incur the cost of a retpoline for now.
+			 * Revisit once static calls are available.
+			 */
+			goto reenter_guest;
+		}
+		exit_fastpath = EXIT_FASTPATH_EXIT_HANDLED;
+	}
+
 	return exit_fastpath;
 }
 

arch/x86/kvm/x86.c

@@ -1608,27 +1608,28 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
 	return 1;
 }
 
-enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
+fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu)
 {
 	u32 msr = kvm_rcx_read(vcpu);
 	u64 data;
-	int ret = 0;
+	fastpath_t ret = EXIT_FASTPATH_NONE;
 
 	switch (msr) {
 	case APIC_BASE_MSR + (APIC_ICR >> 4):
 		data = kvm_read_edx_eax(vcpu);
-		ret = handle_fastpath_set_x2apic_icr_irqoff(vcpu, data);
+		if (!handle_fastpath_set_x2apic_icr_irqoff(vcpu, data)) {
+			kvm_skip_emulated_instruction(vcpu);
+			ret = EXIT_FASTPATH_EXIT_HANDLED;
+               }
 		break;
 	default:
-		return EXIT_FASTPATH_NONE;
+		break;
 	}
 
-	if (!ret) {
+	if (ret != EXIT_FASTPATH_NONE)
 		trace_kvm_msr_write(msr, data);
-		return EXIT_FASTPATH_SKIP_EMUL_INS;
-	}
 
-	return EXIT_FASTPATH_NONE;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(handle_fastpath_set_msr_irqoff);
 
@@ -8205,7 +8206,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	bool req_int_win =
 		dm_request_for_irq_injection(vcpu) &&
 		kvm_cpu_accept_dm_intr(vcpu);
-	enum exit_fastpath_completion exit_fastpath;
+	fastpath_t exit_fastpath;
 
 	bool req_immediate_exit = false;
 

arch/x86/kvm/x86.h

@@ -274,7 +274,7 @@ bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 bool kvm_vector_hashing_enabled(void);
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
-enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
+fastpath_t handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
 
 extern u64 host_xcr0;
 extern u64 supported_xcr0;