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![Sebastian Andrzej Siewior](/assets/img/avatar_default.png)
io_mapping_map_atomic_wc() disables preemption and pagefaults for historical reasons. The conversion to io_mapping_map_local_wc(), which only disables migration, cannot be done wholesale because quite some call sites need to be updated to accommodate with the changed semantics. On PREEMPT_RT enabled kernels the io_mapping_map_atomic_wc() semantics are problematic due to the implicit disabling of preemption which makes it impossible to acquire 'sleeping' spinlocks within the mapped atomic sections. PREEMPT_RT replaces the preempt_disable() with a migrate_disable() for more than a decade. It could be argued that this is a justification to do this unconditionally, but PREEMPT_RT covers only a limited number of architectures and it disables some functionality which limits the coverage further. Limit the replacement to PREEMPT_RT for now. This is also done kmap_atomic(). Link: https://lkml.kernel.org/r/20230310162905.O57Pj7hh@linutronix.de Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Reported-by: Richard Weinberger <richard.weinberger@gmail.com> Link: https://lore.kernel.org/CAFLxGvw0WMxaMqYqJ5WgvVSbKHq2D2xcXTOgMCpgq9nDC-MWTQ@mail.gmail.com Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
231 lines
4.7 KiB
C
231 lines
4.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright © 2008 Keith Packard <keithp@keithp.com>
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*/
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#ifndef _LINUX_IO_MAPPING_H
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#define _LINUX_IO_MAPPING_H
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <linux/bug.h>
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#include <linux/io.h>
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#include <linux/pgtable.h>
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#include <asm/page.h>
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/*
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* The io_mapping mechanism provides an abstraction for mapping
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* individual pages from an io device to the CPU in an efficient fashion.
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*
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* See Documentation/driver-api/io-mapping.rst
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*/
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struct io_mapping {
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resource_size_t base;
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unsigned long size;
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pgprot_t prot;
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void __iomem *iomem;
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};
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#ifdef CONFIG_HAVE_ATOMIC_IOMAP
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#include <linux/pfn.h>
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#include <asm/iomap.h>
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/*
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* For small address space machines, mapping large objects
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* into the kernel virtual space isn't practical. Where
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* available, use fixmap support to dynamically map pages
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* of the object at run time.
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*/
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static inline struct io_mapping *
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io_mapping_init_wc(struct io_mapping *iomap,
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resource_size_t base,
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unsigned long size)
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{
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pgprot_t prot;
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if (iomap_create_wc(base, size, &prot))
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return NULL;
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iomap->base = base;
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iomap->size = size;
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iomap->prot = prot;
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return iomap;
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}
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static inline void
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io_mapping_fini(struct io_mapping *mapping)
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{
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iomap_free(mapping->base, mapping->size);
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}
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/* Atomic map/unmap */
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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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resource_size_t phys_addr;
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BUG_ON(offset >= mapping->size);
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phys_addr = mapping->base + offset;
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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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static inline void
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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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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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io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
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{
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resource_size_t phys_addr;
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BUG_ON(offset >= mapping->size);
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phys_addr = mapping->base + offset;
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return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot);
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}
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static inline void io_mapping_unmap_local(void __iomem *vaddr)
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{
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kunmap_local_indexed((void __force *)vaddr);
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}
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static inline void __iomem *
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io_mapping_map_wc(struct io_mapping *mapping,
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unsigned long offset,
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unsigned long size)
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{
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resource_size_t phys_addr;
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BUG_ON(offset >= mapping->size);
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phys_addr = mapping->base + offset;
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return ioremap_wc(phys_addr, size);
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}
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static inline void
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io_mapping_unmap(void __iomem *vaddr)
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{
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iounmap(vaddr);
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}
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#else /* HAVE_ATOMIC_IOMAP */
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#include <linux/uaccess.h>
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/* Create the io_mapping object*/
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static inline struct io_mapping *
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io_mapping_init_wc(struct io_mapping *iomap,
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resource_size_t base,
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unsigned long size)
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{
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iomap->iomem = ioremap_wc(base, size);
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if (!iomap->iomem)
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return NULL;
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iomap->base = base;
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iomap->size = size;
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iomap->prot = pgprot_writecombine(PAGE_KERNEL);
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return iomap;
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}
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static inline void
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io_mapping_fini(struct io_mapping *mapping)
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{
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iounmap(mapping->iomem);
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}
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/* Non-atomic map/unmap */
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static inline void __iomem *
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io_mapping_map_wc(struct io_mapping *mapping,
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unsigned long offset,
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unsigned long size)
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{
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return mapping->iomem + offset;
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}
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static inline void
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io_mapping_unmap(void __iomem *vaddr)
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{
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}
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/* Atomic map/unmap */
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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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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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static inline void
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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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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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io_mapping_map_local_wc(struct io_mapping *mapping, unsigned long offset)
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{
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return io_mapping_map_wc(mapping, offset, PAGE_SIZE);
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}
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static inline void io_mapping_unmap_local(void __iomem *vaddr)
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{
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io_mapping_unmap(vaddr);
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}
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#endif /* !HAVE_ATOMIC_IOMAP */
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static inline struct io_mapping *
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io_mapping_create_wc(resource_size_t base,
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unsigned long size)
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{
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struct io_mapping *iomap;
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iomap = kmalloc(sizeof(*iomap), GFP_KERNEL);
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if (!iomap)
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return NULL;
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if (!io_mapping_init_wc(iomap, base, size)) {
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kfree(iomap);
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return NULL;
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}
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return iomap;
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}
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static inline void
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io_mapping_free(struct io_mapping *iomap)
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{
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io_mapping_fini(iomap);
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kfree(iomap);
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}
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int io_mapping_map_user(struct io_mapping *iomap, struct vm_area_struct *vma,
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unsigned long addr, unsigned long pfn, unsigned long size);
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#endif /* _LINUX_IO_MAPPING_H */
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