Messages in this thread | | | Date | Wed, 17 Jan 2018 16:29:59 +0000 | From | Dave Martin <> | Subject | Re: [PATCH] arm64: Run enable method for errata work arounds on late CPUs |
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On Wed, Jan 17, 2018 at 02:52:09PM +0000, Suzuki K Poulose wrote: > On 17/01/18 14:38, Dave Martin wrote: > >On Wed, Jan 17, 2018 at 01:22:19PM +0000, Suzuki K Poulose wrote: > >>On 17/01/18 12:25, Dave Martin wrote: > >>>On Wed, Jan 17, 2018 at 10:05:56AM +0000, Suzuki K Poulose wrote:
[...]
> >>>>+ for (; caps->matches; caps++) { > >>>>+ if (cpus_have_cap(caps->capability)) { > >>>>+ if (caps->enable) > >>>>+ caps->enable((void *)caps); > >>> > >>>Do we really need this cast? > >> > >>Yes, otherwise we would be passing a "const *" where a "void *" is expected, > >>and the compiler warns. Or we could simply change the prototype of the > >>enable() method to accept a const capability ptr. > > > >Hmmm, what is this argument for exactly? cpufeature.h doesn't explain > >what it is. > > This was introduced by commit 0a0d111d40fd1 ("arm64: cpufeature: Pass capability > structure to ->enable callback"). > > The idea is to enable multiple entries in the table for a single capability. > Some capabilities (read errata) could be detected in multiple ways. e.g, different > MIDR ranges. (e.g, ARM64_HARDEN_BRANCH_PREDICTOR, ARM64_WORKAROUND_QCOM_FALKOR_E1003. > Now, even though the errata is the same, there might be different work arounds > for them in each "matching" cases. So, we need the "caps" passed on to the > enable() method to see if the "specific work around" should be applied > to the system/CPU (since CPU hwcap could be set by one of the cpu_capabilities > entry.) (as we invoke enable() for all "available" capabilities.) > > Passing the caps information makes it easier to decide, by using the caps->matches().
This makes sense (it's a common OOP idiom anyway: object->method(object, ...))
> > > >Does any enable method use this for anything other than a struct > >arm64_cpu_capabilities const * ? > > No, we use it only for const struct arm64_cpu_capability *. > > >If not, it would be better to specifiy that. > > Yes, that could be done.
OK, I vote for doing that.
Cheers ---Dave
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