From 75fa4adc4f50ee52d8cdfa3e84798176ccb4a354 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Mon, 24 Jan 2022 19:28:58 +0100 Subject: ARM: smp: elide HWCAP_TLS checks or __entry_task updates on SMP+v6 Use the SMP_ON_UP patching framework to elide HWCAP_TLS tests from the context switch and return to userspace code paths, as SMP systems are guaranteed to have this h/w capability. At the same time, omit the update of __entry_task if the system is detected to be UP at runtime, as in that case, the value is never used. Signed-off-by: Ard Biesheuvel --- arch/arm/include/asm/switch_to.h | 4 ++-- arch/arm/include/asm/tls.h | 22 ++++++++++++++++------ 2 files changed, 18 insertions(+), 8 deletions(-) (limited to 'arch/arm/include') diff --git a/arch/arm/include/asm/switch_to.h b/arch/arm/include/asm/switch_to.h index a482c99934ff..f67ae946a3c6 100644 --- a/arch/arm/include/asm/switch_to.h +++ b/arch/arm/include/asm/switch_to.h @@ -3,6 +3,7 @@ #define __ASM_ARM_SWITCH_TO_H #include +#include /* * For v7 SMP cores running a preemptible kernel we may be pre-empted @@ -40,8 +41,7 @@ static inline void set_ti_cpu(struct task_struct *p) do { \ __complete_pending_tlbi(); \ set_ti_cpu(next); \ - if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || \ - IS_ENABLED(CONFIG_SMP)) \ + if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO) || is_smp()) \ __this_cpu_write(__entry_task, next); \ last = __switch_to(prev,task_thread_info(prev), task_thread_info(next)); \ } while (0) diff --git a/arch/arm/include/asm/tls.h b/arch/arm/include/asm/tls.h index d712c170c095..3dcd0f71a0da 100644 --- a/arch/arm/include/asm/tls.h +++ b/arch/arm/include/asm/tls.h @@ -18,22 +18,32 @@ .endm .macro switch_tls_v6, base, tp, tpuser, tmp1, tmp2 +#ifdef CONFIG_SMP +ALT_SMP(nop) +ALT_UP_B(.L0_\@) + .subsection 1 +#endif +.L0_\@: ldr_va \tmp1, elf_hwcap mov \tmp2, #0xffff0fff tst \tmp1, #HWCAP_TLS @ hardware TLS available? streq \tp, [\tmp2, #-15] @ set TLS value at 0xffff0ff0 - mrcne p15, 0, \tmp2, c13, c0, 2 @ get the user r/w register -#ifndef CONFIG_SMP - mcrne p15, 0, \tp, c13, c0, 3 @ yes, set TLS register + beq .L2_\@ + mcr p15, 0, \tp, c13, c0, 3 @ yes, set TLS register +#ifdef CONFIG_SMP + b .L1_\@ + .previous #endif - mcrne p15, 0, \tpuser, c13, c0, 2 @ set user r/w register - strne \tmp2, [\base, #TI_TP_VALUE + 4] @ save it +.L1_\@: switch_tls_v6k \base, \tp, \tpuser, \tmp1, \tmp2 +.L2_\@: .endm .macro switch_tls_software, base, tp, tpuser, tmp1, tmp2 mov \tmp1, #0xffff0fff str \tp, [\tmp1, #-15] @ set TLS value at 0xffff0ff0 .endm +#else +#include #endif #ifdef CONFIG_TLS_REG_EMUL @@ -44,7 +54,7 @@ #elif defined(CONFIG_CPU_V6) #define tls_emu 0 #define has_tls_reg (elf_hwcap & HWCAP_TLS) -#define defer_tls_reg_update IS_ENABLED(CONFIG_SMP) +#define defer_tls_reg_update is_smp() #define switch_tls switch_tls_v6 #elif defined(CONFIG_CPU_32v6K) #define tls_emu 0 -- cgit v1.2.3