175 lines
4.5 KiB
Diff
175 lines
4.5 KiB
Diff
From cfbe235174fa2db1961ea91d3c9f495c930493b9 Mon Sep 17 00:00:00 2001
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Message-Id: <cfbe235174fa2db1961ea91d3c9f495c930493b9.1601675152.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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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 212/333] 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-4.19.148-rt64.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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diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
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index 19c87b52c001..203245dad743 100644
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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 *task)
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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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@@ -549,6 +559,7 @@ int sve_set_vector_length(struct task_struct *task,
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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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@@ -559,8 +570,10 @@ int sve_set_vector_length(struct task_struct *task,
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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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@@ -815,6 +828,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
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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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@@ -828,6 +842,7 @@ asmlinkage void do_sve_acc(unsigned int esr, struct pt_regs *regs)
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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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@@ -894,10 +909,12 @@ void fpsimd_thread_switch(struct task_struct *next)
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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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@@ -906,7 +923,7 @@ 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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@@ -942,6 +959,8 @@ 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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@@ -953,9 +972,11 @@ 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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@@ -1026,6 +1047,7 @@ void fpsimd_restore_current_state(void)
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return;
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}
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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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@@ -1034,6 +1056,7 @@ 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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@@ -1046,6 +1069,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state)
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if (WARN_ON(!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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@@ -1058,6 +1082,7 @@ void fpsimd_update_current_state(struct user_fpsimd_state const *state)
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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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@@ -1104,6 +1129,7 @@ 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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@@ -1117,6 +1143,7 @@ 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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--
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2.17.1
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