From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Thu, 17 Jul 2014 18:10:58 +0100 Subject: [PATCHv4 5/5] arm64: cpuinfo: print info for all CPUs In-Reply-To: References: <1405524767-30220-1-git-send-email-mark.rutland@arm.com> <1405524767-30220-6-git-send-email-mark.rutland@arm.com> <20140716155747.GR29414@arm.com> <53C7A980.8050601@arm.com> <20140717105415.GI21153@arm.com> <20140717123533.GJ21153@arm.com> Message-ID: <20140717171058.GM18203@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 17, 2014 at 02:55:37PM +0100, Peter Maydell wrote: > On 17 July 2014 13:35, Will Deacon wrote: > > We're not denying the possibility of heterogeneity, we're trying to expose a > > consistent view of the system to userspace. Differences between cores should > > be dealt with by the kernel (e.g. IKS, HMP scheduling), not blindly > > passed off to userspace. > > On that basis, why report anything at all about invididual cores? > Just have /proc/cpuinfo report "number of processors: 4" and > no per-CPU information at all... We lost a lot of time on this already (given the internal threads). So my proposal is to go ahead with Mark's patch with per-CPU features. They currently just include the same elf_hwcap multiple times. If we ever need to present different features, the conditions would be: 1. Never report more than elf_hwcap 2. elf_hwcap can only include non-symmetric features *if* Linux gets a way to transparently handle migration or emulation It basically means that Linux would not rely on the user space to make informed decisions on where to run a thread and avoid SIGILL. -- Catalin