>
>
> On 09/12/2016 08:02, Liang Li wrote:
> > Use '||' is more efficient than '|' at this point.
>
> No, it's not, because the check is going to be always false in practice, so the
> || is going to evaluate both branches anyway. So, depending on the
> compiler, either it's the same or it's worse (because a branch is worse than an
> OR instruction).
>
Thanks for clarification.
> If anything, as David said (and if the compiled code changes at all), the "!= 0"
> is superfluous.
>
Yes, it makes the code looks strange.
> Paolo
>
> > Signed-off-by: Liang Li <liang.z.li@xxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index
> > d9c7e98..16c0b00 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -3315,7 +3315,7 @@ static gpa_t
> nonpaging_gva_to_gpa_nested(struct
> > kvm_vcpu *vcpu, gva_t vaddr, {
> > int bit7 = (pte >> 7) & 1, low6 = pte & 0x3f;
> >
> > - return (pte & rsvd_check->rsvd_bits_mask[bit7][level-1]) |
> > + return (pte & rsvd_check->rsvd_bits_mask[bit7][level-1]) ||
> > ((rsvd_check->bad_mt_xwr & (1ull << low6)) != 0); }
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