On Fri, Jan 18, 2019 at 1:22 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> 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")
> 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 adf59fd23a6c..e8e2e289828d 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6472,7 +6472,7 @@ static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
> "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)),
Nice use of a compound literal to avoid a dummy declaration. I haven't
seen that idiom before.
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>
