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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0001-ARM-vfp-Provide-vfp_lock-for-VFP-locking.patch | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/debian/patches-rt/0001-ARM-vfp-Provide-vfp_lock-for-VFP-locking.patch b/debian/patches-rt/0001-ARM-vfp-Provide-vfp_lock-for-VFP-locking.patch new file mode 100644 index 000000000..03eb551db --- /dev/null +++ b/debian/patches-rt/0001-ARM-vfp-Provide-vfp_lock-for-VFP-locking.patch @@ -0,0 +1,75 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Fri, 19 May 2023 16:57:29 +0200 +Subject: [PATCH 1/4] ARM: vfp: Provide vfp_lock() for VFP locking. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +kernel_neon_begin() uses local_bh_disable() to ensure exclusive access +to the VFP unit. This is broken on PREEMPT_RT because a BH disabled +section remains preemptible on PREEMPT_RT. + +Introduce vfp_lock() which uses local_bh_disable() and preempt_disable() +on PREEMPT_RT. Since softirqs are processed always in thread context, +disabling preemption is enough to ensure that the current context won't +get interrupted by something that is using the VFP. Use it in +kernel_neon_begin(). + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + arch/arm/vfp/vfpmodule.c | 32 ++++++++++++++++++++++++++++++-- + 1 file changed, 30 insertions(+), 2 deletions(-) + +--- a/arch/arm/vfp/vfpmodule.c ++++ b/arch/arm/vfp/vfpmodule.c +@@ -56,6 +56,34 @@ extern unsigned int VFP_arch_feroceon __ + union vfp_state *vfp_current_hw_state[NR_CPUS]; + + /* ++ * Claim ownership of the VFP unit. ++ * ++ * The caller may change VFP registers until vfp_unlock() is called. ++ * ++ * local_bh_disable() is used to disable preemption and to disable VFP ++ * processing in softirq context. On PREEMPT_RT kernels local_bh_disable() is ++ * not sufficient because it only serializes soft interrupt related sections ++ * via a local lock, but stays preemptible. Disabling preemption is the right ++ * choice here as bottom half processing is always in thread context on RT ++ * kernels so it implicitly prevents bottom half processing as well. ++ */ ++static void vfp_lock(void) ++{ ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ local_bh_disable(); ++ else ++ preempt_disable(); ++} ++ ++static void vfp_unlock(void) ++{ ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ local_bh_enable(); ++ else ++ preempt_enable(); ++} ++ ++/* + * Is 'thread's most up to date state stored in this CPUs hardware? + * Must be called from non-preemptible context. + */ +@@ -819,7 +847,7 @@ void kernel_neon_begin(void) + unsigned int cpu; + u32 fpexc; + +- local_bh_disable(); ++ vfp_lock(); + + /* + * Kernel mode NEON is only allowed outside of hardirq context with +@@ -850,7 +878,7 @@ void kernel_neon_end(void) + { + /* Disable the NEON/VFP unit. */ + fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); +- local_bh_enable(); ++ vfp_unlock(); + } + EXPORT_SYMBOL(kernel_neon_end); + |