Suzuki K Poulose 143ba05d86 arm64: capabilities: Prepare for fine grained capabilities ... We use arm64_cpu_capabilities to represent CPU ELF HWCAPs exposed to the userspace and the CPU hwcaps used by the kernel, which include cpu features and CPU errata work arounds. Capabilities have some properties that decide how they should be treated : 1) Detection, i.e scope : A cap could be "detected" either : - if it is present on at least one CPU (SCOPE_LOCAL_CPU) Or - if it is present on all the CPUs (SCOPE_SYSTEM) 2) When is it enabled ? - A cap is treated as "enabled" when the system takes some action based on whether the capability is detected or not. e.g, setting some control register, patching the kernel code. Right now, we treat all caps are enabled at boot-time, after all the CPUs are brought up by the kernel. But there are certain caps, which are enabled early during the boot (e.g, VHE, GIC_CPUIF for NMI) and kernel starts using them, even before the secondary CPUs are brought up. We would need a way to describe this for each capability. 3) Conflict on a late CPU - When a CPU is brought up, it is checked against the caps that are known to be enabled on the system (via verify_local_cpu_capabilities()). Based on the state of the capability on the CPU vs. that of System we could have the following combinations of conflict. x-----------------------------x | Type | System | Late CPU | ------------------------------| | a | y | n | ------------------------------| | b | n | y | x-----------------------------x Case (a) is not permitted for caps which are system features, which the system expects all the CPUs to have (e.g VHE). While (a) is ignored for all errata work arounds. However, there could be exceptions to the plain filtering approach. e.g, KPTI is an optional feature for a late CPU as long as the system already enables it. Case (b) is not permitted for errata work arounds which requires some work around, which cannot be delayed. And we ignore (b) for features. Here, yet again, KPTI is an exception, where if a late CPU needs KPTI we are too late to enable it (because we change the allocation of ASIDs etc). So this calls for a lot more fine grained behavior for each capability. And if we define all the attributes to control their behavior properly, we may be able to use a single table for the CPU hwcaps (which cover errata and features, not the ELF HWCAPs). This is a prepartory step to get there. More bits would be added for the properties listed above. We are going to use a bit-mask to encode all the properties of a capabilities. This patch encodes the "SCOPE" of the capability. As such there is no change in how the capabilities are treated. Cc: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Dave Martin <dave.martin@arm.com> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>		2018-03-26 18:01:37 +01:00
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asm	arm64: capabilities: Prepare for fine grained capabilities	2018-03-26 18:01:37 +01:00
uapi/asm	arm64: fpsimd: Fix bad si_code for undiagnosed SIGFPE	2018-03-20 10:03:11 +00:00