[PATCH 5.0 100/122] KVM: VMX: Save RSI to an unused output in the vCPU-run asm blob

From: Greg Kroah-Hartman
Date: Mon May 06 2019 - 10:38:53 EST

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/x86/kvm/vmx/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- 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_vc
"xor %%edi, %%edi \n\t"
"xor %%ebp, %%ebp \n\t"
"pop %%" _ASM_BP "; pop %%" _ASM_DX " \n\t"
+ : 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)),