On Mon, 19 May 2014, li.xi...@freescale.com wrote: > > > For each vmalloc area, there is one guard page at the end of it. > > > so the vm->size = PAGE_ALIGN(offset + request size) + guard page size. > > > > Nope. There is no guard page for statically created vmalloc areas. > > > > Yes, you are right, I'm thinking why the static area has no guard page?
The virtual addresses being used are provided by the static mapping descriptions themselves. Sometimes those mappings are large and contiguous, covering multiple peripherals at once with a single TLB, etc. There is simply no room for a guard page, or no guard page at all between different areas covered by a single section mapping (1MB worth of mapping from a single page table entry). All this to say that trying to enforce a guard page in those cases is likely to throw away all the performance advantage and conplexify things. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
