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Date: Wed, 20 May 2020 05:57:52 +0530 From: Anshuman Khandual <anshuman.khandual@....com> To: Will Deacon <will@...nel.org> Cc: Mark Rutland <mark.rutland@....com>, Suzuki K Poulose <suzuki.poulose@....com>, Catalin Marinas <catalin.marinas@....com>, linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>, Mark Brown <broonie@...nel.org>, Dave Martin <Dave.Martin@....com>, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH V2] arm64/cpuinfo: Move HWCAP name arrays alongside their bit definitions On 05/19/2020 04:05 AM, Will Deacon wrote: > On Fri, May 15, 2020 at 08:58:05AM +0530, Anshuman Khandual wrote: >> On 05/14/2020 01:06 PM, Will Deacon wrote: >>> Why is it a change? We've never reported e.g. "java" on an arm64 kernel, so >> >> We already have "java" defined in existing compat_hwcap_str[] array even >> though it might never get set in compat_elf_hwcap. AFAICS, compat_elf_hwcap >> will have the following capabilities set (at the most). >> >> Via COMPAT_ELF_HWCAP_DEFAULT >> >> 01. COMPAT_HWCAP_HALF >> 02. COMPAT_HWCAP_THUMB >> 03. COMPAT_HWCAP_FAST_MULT >> 04. COMPAT_HWCAP_EDSP >> 05. COMPAT_HWCAP_TLS >> 06. COMPAT_HWCAP_IDIV >> 07. COMPAT_HWCAP_LPAE >> >> Via setup_elf_hwcaps(compat_elf_hwcaps) <-- setup_cpu_features() >> >> 8. COMPAT_HWCAP_NEON >> 9. COMPAT_HWCAP_VFPv4 >> 10. COMPAT_HWCAP_VFP >> 11. COMPAT_HWCAP_VFPv3 >> >> Via arch_timer_set_evtstrm_feature() >> >> 12. COMPAT_HWCAP_EVTSTRM >> >> The code exists for "java" string to be displayed with /proc/cpuinfo but it >> may never get triggered as compat_elf_hwcap will never have JAVA capability >> unless there is a bug as you had rightly mentioned. > > Fair enough, but applying this patch causes a *tonne* of warnings from > aiaiai: > > +In file included from arch/arm64/include/asm/cpufeature.h:11, > + from arch/arm64/include/asm/ptrace.h:11, > + from arch/arm64/include/asm/irqflags.h:10, > + from include/linux/irqflags.h:16, > + from include/linux/spinlock.h:54, > + from include/linux/seqlock.h:36, > + from include/linux/time.h:6, > + from arch/arm64/include/asm/stat.h:12, > + from include/linux/stat.h:6, > + from include/linux/module.h:13, > + from drivers/media/rc/keymaps/rc-imon-mce.mod.c:1: > +arch/arm64/include/asm/hwcap.h:189:26: warning: ‘compat_hwcap2_str’ defined but not used [-Wunused-const-variable=] > + 189 | static const char *const compat_hwcap2_str[] = { > + | ^~~~~~~~~~~~~~~~~ Native default build (defconfig) on arm64 does not throw this warning. I guess this came up with 'make W=n' or something. Anyways if this is indeed an issue, we will have to add in helpers for each HWCAP arrays which will fetch a feature string on index value to be used in c_show (arch/arm64/kernel/cpuinfo.c). I wanted to avoid this to reduce code. > > so I'm dropping this for now. Sure, will respin this later probably after 5.8-rc1.
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