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Commit e75c3c3a authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: VMX: Return VM-Fail from vCPU-run assembly via standard ABI reg 



...to prepare for making the assembly sub-routine callable from C code.

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 77df5495

arch/x86/kvm/vmx/vmenter.S

+8 −8
Original line number Diff line number Diff line
@@ -87,7 +87,7 @@ ENDPROC(vmx_vmexit) 
 * @launched:	%true if the VMCS has been launched

 *

 * Returns:

 *	%RBX is 0 on VM-Exit, 1 on VM-Fail

 *	0 on VM-Exit, 1 on VM-Fail

 */

ENTRY(__vmx_vcpu_run)

	push %_ASM_BP
@@ -163,17 +163,17 @@ ENTRY(__vmx_vcpu_run) 
	mov %r15, VCPU_R15(%_ASM_AX)

#endif



	/* Clear EBX to indicate VM-Exit (as opposed to VM-Fail). */

	xor %ebx, %ebx

	/* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */

	xor %eax, %eax



	/*

	 * Clear all general purpose registers except RSP and RBX to prevent

	 * Clear all general purpose registers except RSP and RAX to prevent

	 * speculative use of the guest's values, even those that are reloaded

	 * via the stack.  In theory, an L1 cache miss when restoring registers

	 * could lead to speculative execution with the guest's values.

	 * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially

	 * free.  RSP and RBX are exempt as RSP is restored by hardware during

	 * VM-Exit and RBX is explicitly loaded with 0 or 1 to "return" VM-Fail.

	 * free.  RSP and RAX are exempt as RSP is restored by hardware during

	 * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.

	 */

1:

#ifdef CONFIG_X86_64
@@ -186,7 +186,7 @@ ENTRY(__vmx_vcpu_run) 
	xor %r14d, %r14d

	xor %r15d, %r15d

#endif

	xor %eax, %eax

	xor %ebx, %ebx

	xor %ecx, %ecx

	xor %edx, %edx

	xor %esi, %esi
@@ -199,6 +199,6 @@ ENTRY(__vmx_vcpu_run) 
	ret



	/* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */

2:	mov $1, %ebx

2:	mov $1, %eax

	jmp 1b

ENDPROC(__vmx_vcpu_run)

arch/x86/kvm/vmx/vmx.c

+4 −4
Original line number Diff line number Diff line
@@ -6446,20 +6446,20 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) 


	asm(

		"call __vmx_vcpu_run \n\t"

	      : ASM_CALL_CONSTRAINT, "=b"(vmx->fail),

	      : ASM_CALL_CONSTRAINT, "=a"(vmx->fail),

#ifdef CONFIG_X86_64

		"=D"((int){0}), "=S"((int){0}), "=d"((int){0})

	      : "D"(vmx), "S"(&vcpu->arch.regs), "d"(vmx->loaded_vmcs->launched)

#else

		"=a"((int){0}), "=d"((int){0}), "=c"((int){0})

		"=d"((int){0}), "=c"((int){0})

	      : "a"(vmx), "d"(&vcpu->arch.regs), "c"(vmx->loaded_vmcs->launched)

#endif

	      : "cc", "memory"

#ifdef CONFIG_X86_64

		, "rax", "rcx"

		, "rbx", "rcx"

		, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"

#else

		, "edi", "esi"

		, "ebx", "edi", "esi"

#endif

	      );