On Mon, Mar 25, 2019 at 10:29:40AM +0100, David Hildenbrand wrote: > On 25.03.19 10:04, Dan Carpenter wrote: > > This code generates a Smatch warning: > > > > arch/x86/kvm/vmx/nested.c:4828 handle_vmfunc() warn: should '(1 << function)' be a 64 bit type? > > > > The warning is generated because "vmcs12->vm_function_control" is a u64 > > but the shift can only test the lower 32 bits. This doesn't cause a > > problem in the current code because we only use BIT(0). This patch just > > silences the static checker warning. > > > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx> > > --- > > arch/x86/kvm/vmx/nested.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > > index f24a2c225070..1f4398246bd9 100644 > > --- a/arch/x86/kvm/vmx/nested.c > > +++ b/arch/x86/kvm/vmx/nested.c > > @@ -4825,7 +4825,7 @@ static int handle_vmfunc(struct kvm_vcpu *vcpu) > > } > > > > vmcs12 = get_vmcs12(vcpu); > > - if ((vmcs12->vm_function_control & (1 << function)) == 0) > > + if ((vmcs12->vm_function_control & (1ULL << function)) == 0) > > I guess one set of parentheses could be dropped here, while touching the > line. The problem is bitwise AND has low precedence so the parenthesis are either required or they improve readability. You could write it like this: if ((vmcs12->vm_function_control & 1ULL << function) == 0) but no one does. > > Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> > Thanks! regards, dan carpenter
