On Wed, Jun 23, 2021 at 02:52:14PM +0800, wubian wrote:
On the arm64, register the uio driver and map a physical spaceThis feels really wrong, shouldn't stuff like this be handled in the
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@xxxxxxxxxxxxx>
---
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
platform itself and not in the driver?
And why is ARM64 special here? Why not other arches? What is odd about
this platform? We almost never want to use #if in .c files, why is it
ok to do that here?
And is this a bugfix? If so, what commit does it fix? Should it go to
stable kernels, and if so, how far back?
I need more information here :)
thanks,
greg k-h