On Wed, Jan 05, 2022 at 01:47:08PM -0700, Yu Zhao wrote:
> On Wed, Jan 05, 2022 at 10:45:26AM +0000, Will Deacon wrote:
> > On Tue, Jan 04, 2022 at 01:22:20PM -0700, Yu Zhao wrote:
> > > diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
> > > index 870c39537dd0..56e4ef5d95fa 100644
> > > --- a/arch/arm64/tools/cpucaps
> > > +++ b/arch/arm64/tools/cpucaps
> > > @@ -36,6 +36,7 @@ HAS_STAGE2_FWB
> > > HAS_SYSREG_GIC_CPUIF
> > > HAS_TLB_RANGE
> > > HAS_VIRT_HOST_EXTN
> > > +HW_AF
> > > HW_DBM
> > > KVM_PROTECTED_MODE
> > > MISMATCHED_CACHE_TYPE
> >
> > As discussed in the previous threads, we really don't need the complexity
> > of the additional cap for the arm64 part. Please can you just use the
> > existing code instead? It's both simpler and, as you say, it's equivalent
> > for existing hardware.
> >
> > That way, this patch just ends up being a renaming exercise and we're all
> > good.
>
> No, renaming alone isn't enough. A caller needs to disable preemption
> before calling system_has_hw_af(), and I don't think it's reasonable
> to ask this caller to do it on x86 as well.
>
> It seems you really prefer not to have HW_AF. So the best I can
> accommodate, considering other potential archs, e.g., risc-v (I do
> plan to provide benchmark results on risc-v, btw), is:
>
> static inline bool arch_has_hw_pte_young(bool local)
> {
> bool hw_af;
>
> if (local) {
> WARN_ON(preemptible());
> return cpu_has_hw_af();
> }
>
> preempt_disable();
> hw_af = system_has_hw_af();
> preempt_enable();
>
> return hw_af;
> }
>
> Or please give me something else I can call without disabling
> preemption, sounds good?
Sure thing, let me take a look. Do you have your series on a public git
tree someplace?
Cheers,
Will
