[PATCH] openrisc: Fix pagewalk usage in arch_dma_{clear, set}_uncached

From: Stafford Horne
Date: Sat Oct 08 2022 - 01:24:37 EST


From: Jann Horn <jannh@xxxxxxxxxx>

Since commit 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page
walker"), walk_page_range() on kernel ranges won't work anymore,
walk_page_range_novma() must be used instead.

Note: I don't have an openrisc development setup, so this is completely
untested.

Fixes: 8782fb61cc848 ("mm: pagewalk: Fix race between unmap and page walker")
Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Stafford Horne <shorne@xxxxxxxxx>
---
Since v1:
- Repost to include LKML.
- Added my SOB
- I tested this by booking this on the qemu virt platform and it works fine.

arch/openrisc/kernel/dma.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
index a82b2caaa560..b3edbb33b621 100644
--- a/arch/openrisc/kernel/dma.c
+++ b/arch/openrisc/kernel/dma.c
@@ -74,10 +74,10 @@ void *arch_dma_set_uncached(void *cpu_addr, size_t size)
* We need to iterate through the pages, clearing the dcache for
* them and setting the cache-inhibit bit.
*/
- mmap_read_lock(&init_mm);
- error = walk_page_range(&init_mm, va, va + size, &set_nocache_walk_ops,
- NULL);
- mmap_read_unlock(&init_mm);
+ mmap_write_lock(&init_mm);
+ error = walk_page_range_novma(&init_mm, va, va + size,
+ &set_nocache_walk_ops, NULL, NULL);
+ mmap_write_unlock(&init_mm);

if (error)
return ERR_PTR(error);
@@ -88,11 +88,11 @@ void arch_dma_clear_uncached(void *cpu_addr, size_t size)
{
unsigned long va = (unsigned long)cpu_addr;

- mmap_read_lock(&init_mm);
+ mmap_write_lock(&init_mm);
/* walk_page_range shouldn't be able to fail here */
- WARN_ON(walk_page_range(&init_mm, va, va + size,
- &clear_nocache_walk_ops, NULL));
- mmap_read_unlock(&init_mm);
+ WARN_ON(walk_page_range_novma(&init_mm, va, va + size,
+ &clear_nocache_walk_ops, NULL, NULL));
+ mmap_write_unlock(&init_mm);
}

void arch_sync_dma_for_device(phys_addr_t addr, size_t size,
--
2.37.2