Messages in this thread | | | Subject | Re: [PATCH 1/2] arm64: capabilities: Allow flexibility in scope | From | Suzuki K Poulose <> | Date | Thu, 8 Feb 2018 16:31:47 +0000 |
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On 08/02/18 16:10, Dave Martin wrote: > On Thu, Feb 08, 2018 at 12:12:37PM +0000, Suzuki K Poulose wrote: >> So far we have restricted the scopes for the capabilities >> as follows : >> 1) Errata workaround check are run all CPUs (i.e, always >> SCOPE_LOCAL_CPU) >> 2) Arm64 features are run only once after the sanitised >> feature registers are available using the SCOPE_SYSTEM. >> >> This prevents detecting cpu features that can be detected >> on one or more CPUs with SCOPE_LOCAL_CPU (e.g KPTI). Similarly >> for errata workaround with SCOPE_SYSTEM. >> >> This patch makes sure that we allow flexibility of having >> any scope for a capability. So, we now run through both >> arm64_features and arm64_errata in two phases for detection: >> >> a) with SCOPE_LOCAL_CPU filter on each boot time enabled >> CPUs. >> b) with SCOPE_SYSTEM filter only once after all boot time >> enabled CPUs are active. >>
>> >> static void update_cpu_ftr_reg(struct arm64_ftr_reg *reg, u64 new) >> @@ -1387,13 +1389,15 @@ static void verify_local_cpu_errata_workarounds(void) >> static void update_cpu_errata_workarounds(void) >> { >> update_cpu_capabilities(arm64_errata, >> - ARM64_CPUCAP_SCOPE_ALL, >> + ARM64_CPUCAP_SCOPE_LOCAL_CPU, > > In isolation, this looks strange because it seems to handle only a > subset of arm64_errata now. > > I think I understand the change as follows: > > * all previously-existing errata workarounds SCOPE_LOCAL_CPU > anyway, so the behavior here doesn't change for any existing > caps; > > * the non SCOPE_SYSTEM workarounds (which this patch prepares for) "the SCOPE_SYSTEM" workarounds..."
> are handled by the new setup_errata_workaround() path.
> > Similarly, the features handling is split into two: one mirroring > the current behaviour (for SCOPE_SYSTEM this time) and one handling> the rest, for supporting SCOPE_CPU_LOCAL features in subsequent > patches.
Right. The changes here are :
New behavior: - Run SCOPE_LOCAL_CPU filter on arm64_features on all CPUs (newly added with this patch) via (newly added)update_cpu_local_features().
Split of existing behavior: - Run SCOPE_LOCAL_CPU(instead of the earlier SCOPE_ALL) on all CPUs in update_cpu_errata_workarounds() - Run SCOPE_SYSTEM filter on arm64_errata, once, via setup_errata_workarounds()
> > Does that sound right? > > I'm not sure we need extra comments or documentation; I just want > to check that I've understood the patch correctly.
So, would you prefer this split to the original patch ?
Cheers Suzuki
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