RSI is clobbered by the VM-Enter asm blob in vmx_vcpu_run(), 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.
Note that this has a funky dependency on removing the 'vmx_return'
global variable definition from vmx_vcpu_run()'s asm blob (done in a
prior patch), as attempting to declare RSI as output would generate a
cryptic compiler error that magically disappeared when vmx_return was
eliminated.
Fixes: 773e8a0425c9 ("x86/kvm: use Enlightened VMCS when running on Hyper-V")
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 5d07d385b637..1821fb9ac009 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6219,7 +6219,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
"xor %%esi, %%esi \n\t"
"xor %%edi, %%edi \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)),
--
2.19.2
