93 lines
3.1 KiB
Diff
93 lines
3.1 KiB
Diff
From be70bbd4d08f00c845633614925c0b126f11a30a Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Fri, 10 Mar 2023 17:29:05 +0100
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Subject: [PATCH 53/62] io-mapping: don't disable preempt on RT in
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io_mapping_map_atomic_wc().
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io_mapping_map_atomic_wc() disables preemption and pagefaults for
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historical reasons. The conversion to io_mapping_map_local_wc(), which
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only disables migration, cannot be done wholesale because quite some call
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sites need to be updated to accommodate with the changed semantics.
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On PREEMPT_RT enabled kernels the io_mapping_map_atomic_wc() semantics are
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problematic due to the implicit disabling of preemption which makes it
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impossible to acquire 'sleeping' spinlocks within the mapped atomic
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sections.
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PREEMPT_RT replaces the preempt_disable() with a migrate_disable() for
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more than a decade. It could be argued that this is a justification to do
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this unconditionally, but PREEMPT_RT covers only a limited number of
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architectures and it disables some functionality which limits the coverage
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further.
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Limit the replacement to PREEMPT_RT for now. This is also done
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kmap_atomic().
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Link: https://lkml.kernel.org/r/20230310162905.O57Pj7hh@linutronix.de
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Reported-by: Richard Weinberger <richard.weinberger@gmail.com>
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Link: https://lore.kernel.org/CAFLxGvw0WMxaMqYqJ5WgvVSbKHq2D2xcXTOgMCpgq9nDC-MWTQ@mail.gmail.com
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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(cherry picked from commit 7eb16f23b9a415f062db22739e59bb144e0b24ab)
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Signed-off-by: Clark Williams <clark.williams@gmail.com>
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---
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include/linux/io-mapping.h | 20 ++++++++++++++++----
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1 file changed, 16 insertions(+), 4 deletions(-)
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diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h
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index 66a774d2710e..b08532b8fba7 100644
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--- a/include/linux/io-mapping.h
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+++ b/include/linux/io-mapping.h
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@@ -69,7 +69,10 @@ io_mapping_map_atomic_wc(struct io_mapping *mapping,
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BUG_ON(offset >= mapping->size);
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phys_addr = mapping->base + offset;
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- preempt_disable();
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+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_disable();
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+ else
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+ migrate_disable();
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pagefault_disable();
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return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
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}
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@@ -79,7 +82,10 @@ io_mapping_unmap_atomic(void __iomem *vaddr)
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{
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kunmap_local_indexed((void __force *)vaddr);
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pagefault_enable();
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- preempt_enable();
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+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_enable();
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+ else
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+ migrate_enable();
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}
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static inline void __iomem *
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@@ -162,7 +168,10 @@ static inline void __iomem *
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io_mapping_map_atomic_wc(struct io_mapping *mapping,
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unsigned long offset)
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{
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- preempt_disable();
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+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_disable();
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+ else
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+ migrate_disable();
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pagefault_disable();
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return io_mapping_map_wc(mapping, offset, PAGE_SIZE);
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}
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@@ -172,7 +181,10 @@ io_mapping_unmap_atomic(void __iomem *vaddr)
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{
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io_mapping_unmap(vaddr);
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pagefault_enable();
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- preempt_enable();
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+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
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+ preempt_enable();
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+ else
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+ migrate_enable();
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}
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static inline void __iomem *
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--
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2.43.0
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