[PATCH] KVM/nVMX: Move nested_vmx_check_vmentry_hw inline assembly to vmenter.S

[Uros Bizjak <ubizjak@gmail.com>]

Move the big inline assembly block from nested_vmx_check_vmentry_hw
to vmenter.S assembly file, taking into account all ABI requirements.

The new function is modelled after __vmx_vcpu_run, and also calls
vmx_update_host_rsp instead of open-coding the function in assembly.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
---
 arch/x86/kvm/vmx/nested.c  | 32 +++-----------------------------
 arch/x86/kvm/vmx/vmenter.S | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1bb6b31eb646..7b26e983e31c 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3012,6 +3012,8 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+bool __nested_vmx_check_vmentry_hw(struct vcpu_vmx *vmx, bool launched);
+
 static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -3050,35 +3052,7 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
 		vmx->loaded_vmcs->host_state.cr4 = cr4;
 	}
 
-	asm(
-		"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */
-		"cmp %%" _ASM_SP ", %c[host_state_rsp](%[loaded_vmcs]) \n\t"
-		"je 1f \n\t"
-		__ex("vmwrite %%" _ASM_SP ", %[HOST_RSP]") "\n\t"
-		"mov %%" _ASM_SP ", %c[host_state_rsp](%[loaded_vmcs]) \n\t"
-		"1: \n\t"
-		"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
-
-		/* Check if vmlaunch or vmresume is needed */
-		"cmpb $0, %c[launched](%[loaded_vmcs])\n\t"
-
-		/*
-		 * VMLAUNCH and VMRESUME clear RFLAGS.{CF,ZF} on VM-Exit, set
-		 * RFLAGS.CF on VM-Fail Invalid and set RFLAGS.ZF on VM-Fail
-		 * Valid.  vmx_vmenter() directly "returns" RFLAGS, and so the
-		 * results of VM-Enter is captured via CC_{SET,OUT} to vm_fail.
-		 */
-		"call vmx_vmenter\n\t"
-
-		CC_SET(be)
-	      : ASM_CALL_CONSTRAINT, CC_OUT(be) (vm_fail)
-	      :	[HOST_RSP]"r"((unsigned long)HOST_RSP),
-		[loaded_vmcs]"r"(vmx->loaded_vmcs),
-		[launched]"i"(offsetof(struct loaded_vmcs, launched)),
-		[host_state_rsp]"i"(offsetof(struct loaded_vmcs, host_state.rsp)),
-		[wordsize]"i"(sizeof(ulong))
-	      : "memory"
-	);
+	vm_fail = __nested_vmx_check_vmentry_hw(vmx, vmx->loaded_vmcs->launched);
 
 	if (vmx->msr_autoload.host.nr)
 		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 799db084a336..9fdcbd9320dc 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -234,6 +234,42 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	jmp 1b
 SYM_FUNC_END(__vmx_vcpu_run)
 
+/**
+ * __nested_vmx_check_vmentry_hw - Run a vCPU via a transition to
+ *				   a nested VMX guest mode
+ * @vmx:	struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
+ * @launched:	%true if the VMCS has been launched
+ *
+ * Returns:
+ *	0 on VM-Exit, 1 on VM-Fail
+ */
+SYM_FUNC_START(__nested_vmx_check_vmentry_hw)
+	push %_ASM_BP
+	mov  %_ASM_SP, %_ASM_BP
+
+	push %_ASM_BX
+
+	/* Copy @launched to BL, _ASM_ARG2 is volatile. */
+	mov %_ASM_ARG2B, %bl
+
+	/* Adjust RSP to account for the CALL to vmx_vmenter(). */
+	lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
+	call vmx_update_host_rsp
+
+	/* Check if vmlaunch or vmresume is needed */
+	cmpb $0, %bl
+
+	/* Enter guest mode */
+	call vmx_vmenter
+
+	/* Return 0 on VM-Exit, 1 on VM-Fail */
+	setbe %al
+
+	pop %_ASM_BX
+
+	pop %_ASM_BP
+	ret
+SYM_FUNC_END(__nested_vmx_check_vmentry_hw)
 
 .section .text, "ax"
 
-- 
2.26.2