[Intel-gfx] [PATCH 4/4] i915: fix remap_io_sg to verify the pgprot

[Christoph Hellwig]

On Mon, May 17, 2021 at 11:46:35PM +0200, Thomas Hellström wrote:
> Apart from the caching aliasing Mattew brought up, doesn't the 
> remap_pfn_range_xxx() family require the mmap_sem held in write mode since 
> it modifies the vma structure? remap_io_sg() is called from the fault 
> handler with the mmap_sem held in read mode only.

Only for vma->vm_flags, and remap_sg already asserts all the interesting
flags are set, although it does not assert VM_IO.

We could move the assignment out of remap_pfn_range_notrack and
into remap_pfn_range and just assert that the proper flags are set,
though.