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Subject[PATCH] uio: Fix bus error that access memory mapped by physical
Date
On the arm64, register the uio driver and map a physical space
on the pci device to user space, then use memset write data to
the address space, a bus error will occur. This error is due to
the dc instruction(cache operation) used in the assembly of memset,
uio mapping physical memory will call pgprot_noncached() to set
non-cached and non-buffered, while pgprot_writecombine() has fewer
restrictions. It does not prohibit write buffer, so replacing
pgprot_noncached() with pgprot_writecombine() can solve this problem.

Signed-off-by: wubian <wubian@uniontech.com>
---
drivers/uio/uio.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index ea96e319c8a0..09b04b20fa30 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -739,7 +739,11 @@ static int uio_mmap_physical(struct vm_area_struct *vma)

vma->vm_ops = &uio_physical_vm_ops;
if (idev->info->mem[mi].memtype == UIO_MEM_PHYS)
+#if defined(CONFIG_ARM64)
+ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+#else
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+#endif

/*
* We cannot use the vm_iomap_memory() helper here,
--
2.20.1


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