linux-kernel - [PATCH v2 03/22] x86/kvm: Replace vmx_vmenter()'s call to kvm_spurious

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Message-Id: <9fc2216c9dc972f95bb65ce2966a682c6bda1cb0.1563413318.git.jpoimboe@redhat.com>
Date:   Wed, 17 Jul 2019 20:36:38 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: [PATCH v2 03/22] x86/kvm: Replace vmx_vmenter()'s call to kvm_spurious_fault() with UD2

Objtool reports the following:

  arch/x86/kvm/vmx/vmenter.o: warning: objtool: vmx_vmenter()+0x14: call without frame pointer save/setup

But frame pointers are necessarily broken anyway, because
__vmx_vcpu_run() clobbers RBP with the guest's value before calling
vmx_vmenter().  So calling without a frame pointer doesn't make things
any worse.

Make objtool happy by changing the call to a UD2.

Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
v2: ud2 instead of kvm_spurious_fault() [Paolo]

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/vmx/vmenter.S | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index d4cb1945b2e3..4010d519eb8c 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -54,9 +54,9 @@ ENTRY(vmx_vmenter)
 	ret
 
 3:	cmpb $0, kvm_rebooting
-	jne 4f
-	call kvm_spurious_fault
-4:	ret
+	je 4f
+	ret
+4:	ud2
 
 	.pushsection .fixup, "ax"
 5:	jmp 3b
-- 
2.20.1