[PATCH 5.15 006/124] dma-mapping: remove bogus test for pfn_valid from dma_map_resource

From: Greg Kroah-Hartman
Date: Tue Apr 26 2022 - 05:07:47 EST

From: Mike Rapoport <rppt@xxxxxxxxxxxxx>

commit a9c38c5d267cb94871dfa2de5539c92025c855d7 upstream.

dma_map_resource() uses pfn_valid() to ensure the range is not RAM.
However, pfn_valid() only checks for availability of the memory map for a
PFN but it does not ensure that the PFN is actually backed by RAM.

As dma_map_resource() is the only method in DMA mapping APIs that has this
check, simply drop the pfn_valid() test from dma_map_resource().

Link: https://lore.kernel.org/all/20210824173741.GC623@xxxxxxx/
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210930013039.11260-2-rppt@xxxxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Fixes: 859a85ddf90e ("mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE")
Link: https://lore.kernel.org/r/Yl0IZWT2nsiYtqBT@xxxxxxxxxxxxx
Signed-off-by: Georgi Djakov <quic_c_gdjako@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
kernel/dma/mapping.c | 4 ----
1 file changed, 4 deletions(-)

--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -296,10 +296,6 @@ dma_addr_t dma_map_resource(struct devic
if (WARN_ON_ONCE(!dev->dma_mask))

- /* Don't allow RAM to be mapped */
- if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
if (dma_map_direct(dev, ops))
addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
else if (ops->map_resource)