Re: [PATCH V2] arm64/cpufeature: Add get_arm64_ftr_reg_nowarn()

Will Deacon
2020-05-26T19:46:56Z

On Tue, May 26, 2020 at 04:01:35PM +0100, Catalin Marinas wrote:
> On Tue, May 26, 2020 at 07:09:13PM +0530, Anshuman Khandual wrote:
> > @@ -632,8 +654,6 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new)
> > const struct arm64_ftr_bits *ftrp;
> > struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg);
> >
> > - BUG_ON(!reg);
> > -
> > for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) {
> > u64 ftr_mask = arm64_ftr_mask(ftrp);
> > s64 ftr_new = arm64_ftr_value(ftrp, new);
> > @@ -762,7 +782,6 @@ static int check_update_ftr_reg(u32 sys_id, int cpu, u64 val, u64 boot)
> > {
> > struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id);
> >
> > - BUG_ON(!regp);
> > update_cpu_ftr_reg(regp, val);
> > if ((boot & regp->strict_mask) == (val & regp->strict_mask))
> > return 0;
> > @@ -776,9 +795,6 @@ static void relax_cpu_ftr_reg(u32 sys_id, int field)
> > const struct arm64_ftr_bits *ftrp;
> > struct arm64_ftr_reg *regp = get_arm64_ftr_reg(sys_id);
> >
> > - if (WARN_ON(!regp))
> > - return;
>
> I think Will wanted an early return in all these functions not just
> removing the BUG_ON(). I'll let him clarify.

Yes, the callers need to check the pointer and return early.

Will