36 lines
1.4 KiB
Diff
36 lines
1.4 KiB
Diff
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Tue, 23 Jan 2024 12:56:21 +0100
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Subject: [PATCH] arm: Disable FAST_GUP on PREEMPT_RT if HIGHPTE is also
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enabled.
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
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gup_pgd_range() is invoked with disabled interrupts and invokes
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__kmap_local_page_prot() via pte_offset_map(), gup_p4d_range().
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With HIGHPTE enabled, __kmap_local_page_prot() invokes kmap_high_get()
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which uses a spinlock_t via lock_kmap_any(). This leads to an
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sleeping-while-atomic error on PREEMPT_RT because spinlock_t becomes a
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sleeping lock and must not be acquired in atomic context.
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The loop in map_new_virtual() uses wait_queue_head_t for wake up which
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also is using a spinlock_t.
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Limit HAVE_FAST_GUP additionaly to remain disabled on PREEMPT_RT with
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HIGHPTE enabled.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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arch/arm/Kconfig | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/arch/arm/Kconfig
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+++ b/arch/arm/Kconfig
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@@ -102,7 +102,7 @@ config ARM
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select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
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select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
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select HAVE_EXIT_THREAD
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- select HAVE_GUP_FAST if ARM_LPAE
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+ select HAVE_GUP_FAST if ARM_LPAE && !(PREEMPT_RT && HIGHPTE)
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select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
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select HAVE_FUNCTION_ERROR_INJECTION
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select HAVE_FUNCTION_GRAPH_TRACER
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