166 lines
4.0 KiB
Diff
166 lines
4.0 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 25 Jul 2018 14:02:38 +0200
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Subject: [PATCH] arm64: fpsimd: use preemp_disable in addition to
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local_bh_disable()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.1-rt3.tar.xz
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In v4.16-RT I noticed a number of warnings from task_fpsimd_load(). The
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code disables BH and expects that it is not preemptible. On -RT the
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task remains preemptible but remains the same CPU. This may corrupt the
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content of the SIMD registers if the task is preempted during
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saving/restoring those registers.
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Add preempt_disable()/enable() to enfore the required semantic on -RT.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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arch/arm64/kernel/fpsimd.c | 31 +++++++++++++++++++++++++++++--
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1 file changed, 29 insertions(+), 2 deletions(-)
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--- a/arch/arm64/kernel/fpsimd.c
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+++ b/arch/arm64/kernel/fpsimd.c
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@@ -159,6 +159,16 @@ static void sve_free(struct task_struct
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__sve_free(task);
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}
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+static void *sve_free_atomic(struct task_struct *task)
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+{
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+ void *sve_state = task->thread.sve_state;
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+
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+ WARN_ON(test_tsk_thread_flag(task, TIF_SVE));
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+
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+ task->thread.sve_state = NULL;
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+ return sve_state;
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+}
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+
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/*
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* TIF_SVE controls whether a task can use SVE without trapping while
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* in userspace, and also the way a task's FPSIMD/SVE state is stored
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@@ -547,6 +557,7 @@ int sve_set_vector_length(struct task_st
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* non-SVE thread.
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*/
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if (task == current) {
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+ preempt_disable();
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local_bh_disable();
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fpsimd_save();
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@@ -557,8 +568,10 @@ int sve_set_vector_length(struct task_st
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if (test_and_clear_tsk_thread_flag(task, TIF_SVE))
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sve_to_fpsimd(task);
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- if (task == current)
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+ if (task == current) {
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local_bh_enable();
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+ preempt_enable();
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+ }
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/*
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* Force reallocation of task SVE state to the correct size
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@@ -813,6 +826,7 @@ asmlinkage void do_sve_acc(unsigned int
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sve_alloc(current);
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+ preempt_disable();
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local_bh_disable();
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fpsimd_save();
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@@ -826,6 +840,7 @@ asmlinkage void do_sve_acc(unsigned int
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WARN_ON(1); /* SVE access shouldn't have trapped */
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local_bh_enable();
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+ preempt_enable();
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}
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/*
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@@ -892,10 +907,12 @@ void fpsimd_thread_switch(struct task_st
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void fpsimd_flush_thread(void)
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{
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int vl, supported_vl;
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+ void *mem = NULL;
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if (!system_supports_fpsimd())
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return;
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+ preempt_disable();
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local_bh_disable();
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memset(¤t->thread.uw.fpsimd_state, 0,
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@@ -904,7 +921,7 @@ void fpsimd_flush_thread(void)
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if (system_supports_sve()) {
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clear_thread_flag(TIF_SVE);
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- sve_free(current);
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+ mem = sve_free_atomic(current);
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/*
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* Reset the task vector length as required.
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@@ -940,6 +957,8 @@ void fpsimd_flush_thread(void)
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set_thread_flag(TIF_FOREIGN_FPSTATE);
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local_bh_enable();
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+ preempt_enable();
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+ kfree(mem);
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}
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/*
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@@ -951,9 +970,11 @@ void fpsimd_preserve_current_state(void)
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if (!system_supports_fpsimd())
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return;
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+ preempt_disable();
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local_bh_disable();
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fpsimd_save();
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local_bh_enable();
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+ preempt_enable();
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}
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/*
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@@ -1011,6 +1032,7 @@ void fpsimd_restore_current_state(void)
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if (!system_supports_fpsimd())
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return;
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+ preempt_disable();
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local_bh_disable();
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if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
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@@ -1019,6 +1041,7 @@ void fpsimd_restore_current_state(void)
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}
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local_bh_enable();
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+ preempt_enable();
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}
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/*
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@@ -1031,6 +1054,7 @@ void fpsimd_update_current_state(struct
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if (!system_supports_fpsimd())
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return;
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+ preempt_disable();
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local_bh_disable();
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current->thread.uw.fpsimd_state = *state;
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@@ -1043,6 +1067,7 @@ void fpsimd_update_current_state(struct
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clear_thread_flag(TIF_FOREIGN_FPSTATE);
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local_bh_enable();
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+ preempt_enable();
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}
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/*
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@@ -1088,6 +1113,7 @@ void kernel_neon_begin(void)
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BUG_ON(!may_use_simd());
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+ preempt_disable();
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local_bh_disable();
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__this_cpu_write(kernel_neon_busy, true);
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@@ -1101,6 +1127,7 @@ void kernel_neon_begin(void)
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preempt_disable();
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local_bh_enable();
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+ preempt_enable();
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}
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EXPORT_SYMBOL(kernel_neon_begin);
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