Messages in this thread | | | Date | Wed, 18 Oct 2023 13:43:27 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH v2 3/3] arm64: cpufeature: Change 32-bit EL0 to display enabled cores |
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On Tue, 17 Oct 2023 20:15:43 +0100, Jeremy Linton <jeremy.linton@arm.com> wrote: > > Hi, > > On 10/17/23 13:01, Marc Zyngier wrote: > > On Tue, 17 Oct 2023 06:23:22 +0100, > > Jeremy Linton <jeremy.linton@arm.com> wrote: > >> > >> Now that we have the ability to display the list of cores > >> with a feature when it is selectivly enabled, lets display the > >> cores enabled for 32-bit use at EL0. > >> > >> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> > >> --- > >> arch/arm64/kernel/cpufeature.c | 15 +++++++++++++-- > >> 1 file changed, 13 insertions(+), 2 deletions(-) > >> > >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > >> index b7b67bac0e60..512cbe446b41 100644 > >> --- a/arch/arm64/kernel/cpufeature.c > >> +++ b/arch/arm64/kernel/cpufeature.c > >> @@ -1533,8 +1533,17 @@ static bool has_32bit_el0(const struct arm64_cpu_capabilities *entry, int scope) > >> if (!has_cpuid_feature(entry, scope)) > >> return allow_mismatched_32bit_el0; > >> - if (scope == SCOPE_SYSTEM) > >> - pr_info("detected: 32-bit EL0 Support\n"); > >> + if (scope == SCOPE_SYSTEM) { > >> + struct arm64_cpu_capabilities *has_32bit; > >> + > >> + has_32bit = (struct arm64_cpu_capabilities *)entry; > >> + > >> + has_32bit->cpus = system_32bit_el0_cpumask(); > > > > This seems rather dodgy. 'entry' comes from a static const array which > > will, in all likelihood be mapped R/O pretty soon after the initial > > CPU bringup. Try offlining/onlining a CPU and you should see a > > firework similar to what I have below (I hacked the CnP property, but > > that's no different from what you are doing): > > Yes, dodgy is a good word. The other choices, maintain a mask just for > the print or dump the static key and always use the cpu_32bit_el0_mask > or some combination, weren't much better in the "ick" category. If > anyone sees a better way I'm open to suggestion, although simply > dropping this last patch is fine too.
An obvious choice would be to replace the 'cpus' cpumask with a function that evaluates a cpumask stored separately.
M.
-- Without deviation from the norm, progress is not possible.
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