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: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index a3d9a8e..e06a3f3 100644 (file)
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -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)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1b73a82..9a1d27e 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -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
              );