On Thu, Nov 19, 2020 at 10:57:47PM +0800, liwei (GF) wrote:
> On 2020/10/2 18:57, Will Deacon wrote:
> > On Wed, Sep 30, 2020 at 05:31:35PM +0800, Wei Li wrote:
> >> @@ -80,6 +80,15 @@ struct arm_spe_pmu {
> >> /* Keep track of our dynamic hotplug state */
> >> static enum cpuhp_state arm_spe_pmu_online;
> >>
> >> +static u64 sys_pmsevfr_el1_mask[] = {
> >> + [ID_AA64DFR0_PMSVER_8_2] = GENMASK_ULL(63, 48) | GENMASK_ULL(31, 24) |
> >> + GENMASK_ULL(15, 12) | BIT_ULL(7) | BIT_ULL(5) | BIT_ULL(3) |
> >> + BIT_ULL(1),
> >> + [ID_AA64DFR0_PMSVER_8_3] = GENMASK_ULL(63, 48) | GENMASK_ULL(31, 24) |
> >> + GENMASK_ULL(18, 17) | GENMASK_ULL(15, 11) | BIT_ULL(7) |
> >> + BIT_ULL(5) | BIT_ULL(3) | BIT_ULL(1),
> >> +};
> >
> > Ok, so I finally figured out what I don't like about this: it's the fact
> > that the RES0 mask only ever reduces, but we have no way of ensuring that
> > by construction with this approach. In other words, it's a bit brittle to
> > keep all of these things defined entirely separately from one another.
> >
> > How about a small change so that we define things like:
> >
> > #define SYS_PMSEVFR_EL1_RES0_8_2 SYS_PMSEVFR_EL1_RES0 &
> > ~(...)
> >
> > #define SYS_PMSEVFR_EL1_RES0_8_3 SYS_PMSEVFR_EL1_RES0_8_2 &
> > ~(...)
> >
> > where the '...' parts identify the bits that are no longer RES0 for that
> > version of the architecture?
> >
>
> Sorry for the long delay.
>
> These is also an array-index-out-of-bounds issue when accessing
> 'sys_pmsevfr_el1_mask', if
> the pmsver read in the future is bigger than what the driver supports.
>
> So how about change to:
>
> static u64 arm_spe_pmsevfr_mask(u16 pmsver)
> {
> u64 mask = 0;
>
> if (pmsver >= ID_AA64DFR0_PMSVER_8_3)
> mask |= BIT_ULL(18) | BIT_ULL(17) | BIT_ULL(11);
> if (pmsver >= ID_AA64DFR0_PMSVER_8_2)
> mask |= GENMASK_ULL(63, 48) | GENMASK_ULL(31, 24) |
> GENMASK_ULL(15, 12) | BIT_ULL(7) | BIT_ULL(5) |
> BIT_ULL(3) |
> BIT_ULL(1);
> return mask;
> }
>
> Thus, the driver can try its best to support, and the definition is clear
> enough to show
> the difference between versions of SPE.
>
> Or should i still define them as what you advised and add a check of pmsver
> to just serve
> the versions what the driver support?
I think I'd prefer that, yes.
Will
