KVM: VMX: Save RSI to an unused output in the vCPU-run asm blob

commit f3689e3f17f064fd4cd5f0cb01ae2395c94f39d9 upstream.

RSI is clobbered by the vCPU-run asm blob, but it's not marked as such,
probably because GCC doesn't let you mark inputs as clobbered.  "Save"
RSI to a dummy output so that GCC recognizes it as being clobbered.

Fixes: 773e8a0425c9 ("x86/kvm: use Enlightened VMCS when running on Hyper-V")
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 72f1d17711f24f398bf60a4ae044baa463cb4cc3..da6fdd5434a17db6b1e9253e9f9a180f628799bf 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6465,7 +6465,7 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
                "xor %%edi, %%edi \n\t"
                "xor %%ebp, %%ebp \n\t"
                "pop  %%" _ASM_BP "; pop  %%" _ASM_DX " \n\t"
-             : ASM_CALL_CONSTRAINT
+             : ASM_CALL_CONSTRAINT, "=S"((int){0})
              : "c"(vmx), "d"((unsigned long)HOST_RSP), "S"(evmcs_rsp),
                [launched]"i"(offsetof(struct vcpu_vmx, __launched)),
                [fail]"i"(offsetof(struct vcpu_vmx, fail)),