Re: [PATCH 1/2] dma-mapping: remove bogus test for pfn_valid from dma_map_resource

[Christoph Hellwig]

On Thu, Sep 30, 2021 at 04:30:38AM +0300, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> 
> 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>

We'll lose a bit of a sanity check with this, but given the problems it
caused:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>