linux-kernel - [PATCH 2/2] x86/kvm: Add output operand in vmx_handle_external

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Date:	Fri, 22 Jan 2016 15:44:38 -0600
From:	Chris J Arges <chris.j.arges@...onical.com>
To:	jpoimboe@...hat.com, live-patching@...r.kernel.org, x86@...nel.org,
	pbonzini@...hat.com
Cc:	gleb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Chris J Arges <chris.j.arges@...onical.com>
Subject: [PATCH 2/2] x86/kvm: Add output operand in vmx_handle_external_intr inline asm

Stacktool generates the following warning:
  stacktool: arch/x86/kvm/vmx.o: vmx_handle_external_intr()+0x67: call without frame pointer save/setup

By adding the stackpointer as an output operand, this patch ensures that a
stack frame is created when CONFIG_FRAME_POINTER is enabled for the inline
assmebly statement.

Signed-off-by: Chris J Arges <chris.j.arges@...onical.com>
---
 arch/x86/kvm/vmx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e2951b6..e153522 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8356,6 +8356,7 @@ static void vmx_complete_atomic_exit(struct vcpu_vmx *vmx)
 static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
 {
 	u32 exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	register void *__sp asm(_ASM_SP);
 
 	/*
 	 * If external interrupt exists, IF bit is set in rflags/eflags on the
@@ -8388,8 +8389,9 @@ static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
 			"call *%[entry]\n\t"
 			:
 #ifdef CONFIG_X86_64
-			[sp]"=&r"(tmp)
+			[sp]"=&r"(tmp),
 #endif
+			"+r"(__sp)
 			:
 			[entry]"r"(entry),
 			[ss]"i"(__KERNEL_DS),
-- 
2.5.0