diff options
Diffstat (limited to 'patches/arm64-cpufeature-don-t-use-mutex-in-bringup-path.patch')
| -rw-r--r-- | patches/arm64-cpufeature-don-t-use-mutex-in-bringup-path.patch | 169 |
1 files changed, 0 insertions, 169 deletions
diff --git a/patches/arm64-cpufeature-don-t-use-mutex-in-bringup-path.patch b/patches/arm64-cpufeature-don-t-use-mutex-in-bringup-path.patch deleted file mode 100644 index ce4f85545922..000000000000 --- a/patches/arm64-cpufeature-don-t-use-mutex-in-bringup-path.patch +++ /dev/null @@ -1,169 +0,0 @@ -From: Mark Rutland <mark.rutland@arm.com> -Date: Tue, 16 May 2017 15:18:05 +0100 -Subject: [PATCH] arm64/cpufeature: don't use mutex in bringup path - -Commit b2bb439ad99a1497daa392a527c0e52c69915ce9 upstream - -Currently, cpus_set_cap() calls static_branch_enable_cpuslocked(), which -must take the jump_label mutex. - -We call cpus_set_cap() in the secondary bringup path, from the idle -thread where interrupts are disabled. Taking a mutex in this path "is a -NONO" regardless of whether it's contended, and something we must avoid. -We didn't spot this until recently, as ___might_sleep() won't warn for -this case until all CPUs have been brought up. - -This patch avoids taking the mutex in the secondary bringup path. The -poking of static keys is deferred until enable_cpu_capabilities(), which -runs in a suitable context on the boot CPU. To account for the static -keys being set later, cpus_have_const_cap() is updated to use another -static key to check whether the const cap keys have been initialised, -falling back to the caps bitmap until this is the case. - -This means that users of cpus_have_const_cap() gain should only gain a -single additional NOP in the fast path once the const caps are -initialised, but should always see the current cap value. - -The hyp code should never dereference the caps array, since the caps are -initialized before we run the module initcall to initialise hyp. A check -is added to the hyp init code to document this requirement. - -This change will sidestep a number of issues when the upcoming hotplug -locking rework is merged. - -Signed-off-by: Mark Rutland <mark.rutland@arm.com> -Reviewed-by: Marc Zyniger <marc.zyngier@arm.com> -Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com> -Acked-by: Will Deacon <will.deacon@arm.com> -Cc: Christoffer Dall <christoffer.dall@linaro.org> -Cc: Peter Zijlstra <peterz@infradead.org> -Cc: Sebastian Sewior <bigeasy@linutronix.de> -Cc: Thomas Gleixner <tglx@linutronix.de> -Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ---- - arch/arm64/include/asm/cpufeature.h | 12 ++++++++++-- - arch/arm64/include/asm/kvm_host.h | 8 ++++++-- - arch/arm64/kernel/cpufeature.c | 23 +++++++++++++++++++++-- - 3 files changed, 37 insertions(+), 6 deletions(-) - ---- a/arch/arm64/include/asm/cpufeature.h -+++ b/arch/arm64/include/asm/cpufeature.h -@@ -115,6 +115,7 @@ struct arm64_cpu_capabilities { - - extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS); - extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS]; -+extern struct static_key_false arm64_const_caps_ready; - - bool this_cpu_has_cap(unsigned int cap); - -@@ -124,7 +125,7 @@ static inline bool cpu_have_feature(unsi - } - - /* System capability check for constant caps */ --static inline bool cpus_have_const_cap(int num) -+static inline bool __cpus_have_const_cap(int num) - { - if (num >= ARM64_NCAPS) - return false; -@@ -138,6 +139,14 @@ static inline bool cpus_have_cap(unsigne - return test_bit(num, cpu_hwcaps); - } - -+static inline bool cpus_have_const_cap(int num) -+{ -+ if (static_branch_likely(&arm64_const_caps_ready)) -+ return __cpus_have_const_cap(num); -+ else -+ return cpus_have_cap(num); -+} -+ - static inline void cpus_set_cap(unsigned int num) - { - if (num >= ARM64_NCAPS) { -@@ -145,7 +154,6 @@ static inline void cpus_set_cap(unsigned - num, ARM64_NCAPS); - } else { - __set_bit(num, cpu_hwcaps); -- static_branch_enable(&cpu_hwcap_keys[num]); - } - } - ---- a/arch/arm64/include/asm/kvm_host.h -+++ b/arch/arm64/include/asm/kvm_host.h -@@ -24,6 +24,7 @@ - - #include <linux/types.h> - #include <linux/kvm_types.h> -+#include <asm/cpufeature.h> - #include <asm/kvm.h> - #include <asm/kvm_asm.h> - #include <asm/kvm_mmio.h> -@@ -356,9 +357,12 @@ static inline void __cpu_init_hyp_mode(p - unsigned long vector_ptr) - { - /* -- * Call initialization code, and switch to the full blown -- * HYP code. -+ * Call initialization code, and switch to the full blown HYP code. -+ * If the cpucaps haven't been finalized yet, something has gone very -+ * wrong, and hyp will crash and burn when it uses any -+ * cpus_have_const_cap() wrapper. - */ -+ BUG_ON(!static_branch_likely(&arm64_const_caps_ready)); - __kvm_call_hyp((void *)pgd_ptr, hyp_stack_ptr, vector_ptr); - } - ---- a/arch/arm64/kernel/cpufeature.c -+++ b/arch/arm64/kernel/cpufeature.c -@@ -975,8 +975,16 @@ void update_cpu_capabilities(const struc - */ - void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps) - { -- for (; caps->matches; caps++) -- if (caps->enable && cpus_have_cap(caps->capability)) -+ for (; caps->matches; caps++) { -+ unsigned int num = caps->capability; -+ -+ if (!cpus_have_cap(num)) -+ continue; -+ -+ /* Ensure cpus_have_const_cap(num) works */ -+ static_branch_enable(&cpu_hwcap_keys[num]); -+ -+ if (caps->enable) { - /* - * Use stop_machine() as it schedules the work allowing - * us to modify PSTATE, instead of on_each_cpu() which -@@ -984,6 +992,8 @@ void __init enable_cpu_capabilities(cons - * we return. - */ - stop_machine(caps->enable, NULL, cpu_online_mask); -+ } -+ } - } - - /* -@@ -1086,6 +1096,14 @@ static void __init setup_feature_capabil - enable_cpu_capabilities(arm64_features); - } - -+DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready); -+EXPORT_SYMBOL(arm64_const_caps_ready); -+ -+static void __init mark_const_caps_ready(void) -+{ -+ static_branch_enable(&arm64_const_caps_ready); -+} -+ - /* - * Check if the current CPU has a given feature capability. - * Should be called from non-preemptible context. -@@ -1112,6 +1130,7 @@ void __init setup_cpu_features(void) - /* Set the CPU feature capabilies */ - setup_feature_capabilities(); - enable_errata_workarounds(); -+ mark_const_caps_ready(); - setup_elf_hwcaps(arm64_elf_hwcaps); - - if (system_supports_32bit_el0()) |