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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel