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

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Date:   Tue, 26 Apr 2022 10:20:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>,
        Christoph Hellwig <hch@....de>,
        David Hildenbrand <david@...hat.com>,
        Will Deacon <will@...nel.org>,
        Georgi Djakov <quic_c_gdjako@...cinc.com>
Subject: [PATCH 5.15 006/124] dma-mapping: remove bogus test for pfn_valid from dma_map_resource

From: Mike Rapoport <rppt@...ux.ibm.com>

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@arm.com/
Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: David Hildenbrand <david@...hat.com>
Link: https://lore.kernel.org/r/20210930013039.11260-2-rppt@kernel.org
Signed-off-by: Will Deacon <will@...nel.org>
Fixes: 859a85ddf90e ("mm: remove pfn_valid_within() and CONFIG_HOLES_IN_ZONE")
Link: https://lore.kernel.org/r/Yl0IZWT2nsiYtqBT@linux.ibm.com
Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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))
 		return DMA_MAPPING_ERROR;
 
-	/* Don't allow RAM to be mapped */
-	if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
-		return DMA_MAPPING_ERROR;
-
 	if (dma_map_direct(dev, ops))
 		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
 	else if (ops->map_resource)