Commit b4fc36e6 authored by Shawn Anastasio's avatar Shawn Anastasio Committed by Michael Ellerman

powerpc/dma: Fix invalid DMA mmap behavior

The refactor of powerpc DMA functions in commit 6666cc17
("powerpc/dma: remove dma_nommu_mmap_coherent") incorrectly
changes the way DMA mappings are handled on powerpc.
Since this change, all mapped pages are marked as cache-inhibited
through the default implementation of arch_dma_mmap_pgprot.
This differs from the previous behavior of only marking pages
in noncoherent mappings as cache-inhibited and has resulted in
sporadic system crashes in certain hardware configurations and
workloads (see Bugzilla).

This commit restores the previous correct behavior by providing
an implementation of arch_dma_mmap_pgprot that only marks
pages in noncoherent mappings as cache-inhibited. As this behavior
should be universal for all powerpc platforms a new file,
dma-generic.c, was created to store it.

Fixes: 6666cc17 ("powerpc/dma: remove dma_nommu_mmap_coherent")
# NOTE: fixes commit 6666cc17 released in v5.1.
# Consider a stable tag:
# Cc: stable@vger.kernel.org # v5.1+
# NOTE: fixes commit 6666cc17 released in v5.1.
# Consider a stable tag:
# Cc: stable@vger.kernel.org # v5.1+
Cc: stable@vger.kernel.org # v5.1+
Signed-off-by: default avatarShawn Anastasio <shawn@anastas.io>
Reviewed-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190717235437.12908-1-shawn@anastas.io
parent 9798f4ea
......@@ -121,6 +121,7 @@ config PPC
select ARCH_32BIT_OFF_T if PPC32
select ARCH_HAS_DEBUG_VIRTUAL
select ARCH_HAS_DEVMEM_IS_ALLOWED
select ARCH_HAS_DMA_MMAP_PGPROT
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
......
......@@ -49,7 +49,8 @@ obj-y := cputable.o ptrace.o syscalls.o \
signal.o sysfs.o cacheinfo.o time.o \
prom.o traps.o setup-common.o \
udbg.o misc.o io.o misc_$(BITS).o \
of_platform.o prom_parse.o
of_platform.o prom_parse.o \
dma-common.o
obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
signal_64.o ptrace32.o \
paca.o nvram_64.o firmware.o
......
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Contains common dma routines for all powerpc platforms.
*
* Copyright (C) 2019 Shawn Anastasio.
*/
#include <linux/mm.h>
#include <linux/dma-noncoherent.h>
pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
unsigned long attrs)
{
if (!dev_is_dma_coherent(dev))
return pgprot_noncached(prot);
return prot;
}
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