kernel.git/arch/powerpc/include/asm/cpu_has_feature.h, branch linux-4.10.y

powerpc: Fix build failure with clang due to BUILD_BUG_ON()

2017-01-25T02:36:10Z

Anton says: In commit 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()") and commit c12e6f24d413 ("powerpc: Add option to use jump label for mmu_has_feature()") we added: BUILD_BUG_ON(!__builtin_constant_p(feature)) to cpu_has_feature() and mmu_has_feature() in order to catch usage issues (such as cpu_has_feature(cpu_has_feature(X), which has happened once in the past). Unfortunately LLVM isn't smart enough to resolve this, and it errors out. I work around it in my clang/LLVM builds of the kernel, but I have just discovered that it causes a lot of issues for the bcc (eBPF) trace tool (which uses LLVM). For now just #ifdef it away for clang builds. Fixes: 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()") Fixes: c12e6f24d413 ("powerpc: Add option to use jump label for mmu_has_feature()") Cc: stable@vger.kernel.org # v4.8+ Reported-by: Anton Blanchard Tested-by: Naveen N. Rao Signed-off-by: Michael Ellerman

powerpc/kernel: Fix size of NUM_CPU_FTR_KEYS on 32-bit

2016-09-12T02:48:28Z

The number of CPU feature keys is meant to map 1:1 to the number of CPU feature flags defined in cputable.h, and the latter must fit in an unsigned long. In commit 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()"), I incorrectly defined NUM_CPU_FTR_KEYS to 64. There should be no real adverse consequences of this bug, other than us allocating too many keys. Fix it by using BITS_PER_LONG. Fixes: 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()") Tested-by: Meelis Roos Signed-off-by: Michael Ellerman

powerpc/mm: Catch usage of cpu/mmu_has_feature() before jump label init

2016-08-01T01:15:06Z

This allows us to catch incorrect usage of cpu_has_feature() and mmu_has_feature() prior to jump labels being initialised. mpe: Use printk() and dump_stack() rather than WARN_ON(), because WARN_ON() may not work this early in boot. Rename the Kconfig. Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc: Add option to use jump label for mmu_has_feature()

2016-08-01T01:15:06Z

As we just did for CPU features. Signed-off-by: Kevin Hao Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc: Add option to use jump label for cpu_has_feature()

2016-08-01T01:15:05Z

We do binary patching of asm code using CPU features, which is a one-time operation, done during early boot. However checks of CPU features in C code are currently done at run time, even though the set of CPU features can never change after boot. We can optimise this by using jump labels to implement cpu_has_feature(), meaning checks in C code are binary patched into a single nop or branch. For a C sequence along the lines of: if (cpu_has_feature(FOO)) return 2; The generated code before is roughly: ld r9,-27640(r2) ld r9,0(r9) lwz r9,32(r9) cmpwi cr7,r9,0 bge cr7, 1f li r3,2 blr 1: ... After (true): nop li r3,2 blr After (false): b 1f li r3,2 blr 1: ... mpe: Rename MAX_CPU_FEATURES as we already have a #define with that name, and define it simply as a constant, rather than doing tricks with sizeof and NULL pointers. Rename the array to cpu_feature_keys. Use the kconfig we added to guard it. Add BUILD_BUG_ON() if the feature is not a compile time constant. Rewrite the change log. Signed-off-by: Kevin Hao Signed-off-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman

powerpc: Move cpu_has_feature() to a separate file

2016-08-01T01:15:03Z

We plan to use jump label for cpu_has_feature(). In order to implement this we need to include the linux/jump_label.h in asm/cputable.h. Unfortunately if we do that it leads to an include loop. The root of the problem seems to be that reg.h needs cputable.h (for CPU_FTRs), and then cputable.h via jump_label.h eventually pulls in hw_irq.h which needs reg.h (for MSR_EE). So move cpu_has_feature() to a separate file on its own. Signed-off-by: Kevin Hao Signed-off-by: Aneesh Kumar K.V [mpe: Rename to cpu_has_feature.h and flesh out change log] Signed-off-by: Michael Ellerman