3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: "Maciej W. Rozycki" macro@linux-mips.org
commit 03dce595270f22d59a6f37e9170287c1afd94bc2 upstream.
Fix "BUG: using smp_processor_id() in preemptible" reported in accesses to thread's FPU defaults: the value to initialise FSCR to at program startup, the FCSR r/w mask and the contents of FIR in full FPU emulation, removing a regression introduced with 9b26616c [MIPS: Respect the ISA level in FCSR handling] and f6843626 [MIPS: math-emu: Set FIR feature flags for full emulation].
Use `boot_cpu_data' to obtain the data from, following the approach that `cpu_has_*' macros take and avoiding the call to `smp_processor_id' made in the reference to `current_cpu_data'. The contents of FSCR have to be consistent across processors in an SMP system, the settings there must not change as a thread is migrated across processors. And the contents of FIR are guaranteed to be consistent in FPU emulation, by definition.
Signed-off-by: Maciej W. Rozycki macro@linux-mips.org Tested-by: Ezequiel Garcia ezequiel.garcia@imgtec.com Tested-by: Paul Martin paul.martin@codethink.co.uk Cc: Markos Chandras Markos.Chandras@imgtec.com Cc: James Hogan james.hogan@imgtec.com Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/10030/ Signed-off-by: Ralf Baechle ralf@linux-mips.org [bwh: Backported to 3.16: - Drop change in cop1_cfc() - Adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/arch/mips/include/asm/elf.h +++ b/arch/mips/include/asm/elf.h @@ -277,7 +277,7 @@ do { \ \ current->thread.abi = &mips_abi; \ \ - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \ + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \ } while (0)
#endif /* CONFIG_32BIT */ @@ -337,7 +337,7 @@ do { \ else \ current->thread.abi = &mips_abi; \ \ - current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \ + current->thread.fpu.fcr31 = boot_cpu_data.fpu_csr31; \ \ p = personality(current->personality); \ if (p != PER_LINUX32 && p != PER_LINUX) \ --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -177,7 +177,7 @@ int ptrace_setfpregs(struct task_struct
__get_user(value, data + 64); fcr31 = child->thread.fpu.fcr31; - mask = current_cpu_data.fpu_msk31; + mask = boot_cpu_data.fpu_msk31; child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask);
/* FIR may not be written. */ --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -934,7 +934,7 @@ emul: * Preserve read-only bits, * and convert to ieee library modes */ - mask = current_cpu_data.fpu_msk31; + mask = boot_cpu_data.fpu_msk31; ctx->fcr31 = (value & ~(mask | FPU_CSR_RM)) | (ctx->fcr31 & mask) | modeindex(value);