VME driver patch for PowerPC

[Heater, Daniel (GE Infrastructure)]

> +#ifdef CONFIG_PPC32
> +       vma->vm_page_prot.pgprot |= _PAGE_NO_CACHE | _PAGE_GUARDED;
> +       DPRINTF("PowerPC protection flags set.\n");
> +#endif

Cool. I was just about to suggest _PAGE_NO_CACHE | _PAGE_GUARDED.

>          /* Don't swap these pages out
>           */
> -       vma->vm_flags |= VM_RESERVED;
> +       vma->vm_flags |= VM_LOCKED | VM_IO | VM_SHM;

I'm trying to understand this change. VM_IO looks like it needs to
be there to prevent deadlocks on core dumps.
http://www.uwsg.iu.edu/hypermail/linux/kernel/0202.0/1309.html

and if I'm interpreting some older mailing list postings correctly,
VM_RESERVED is a replacement for VM_LOCKED | VM_SHM but VM_RESERVED
may yield some performance advantages. Thus, in later kernels you
only see VM_RESERVED and not VM_LOCKED | VM_SHM.

Maybe since this is an out of tree driver, it should have
> +       vma->vm_flags |= VM_LOCKED | VM_IO | VM_SHM | VM_RESERVED;

to handle older kernels and still get the advantages of VM_RESERVED
on newer kernels.

What do you think? Am I interpreting this correctly?

Daniel.

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