Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx> writes: > Eric W. Biederman wrote: >> Consider a memory hole of size 8M immediately after our bootmem bitmap. >> head.S which knows nothing of holes will map the pages of the hole >> into the initial page tables assuming that is where the page tables >> will live. >> > > Sure, but considering we're only talking about mapping an additional *2* > pages, the chances are that it will affect a kernel as much as the early > head.S mapping. It's well within the variability of fairly similar > kernel configs. If (cpu_has_pse) it may only be an additional two pages. INIT_MAP_BEYOND is currently mapping a lot more then that. >> As for how to fix this, we need to call boot_ioremap or better >> bt_ioremap on the address returned from alloc_bootmem_pages_low to >> force the allocated page into the page table. After we have setup >> the page table page we can call unmap the page to free up the scarce >> early mapping resource. >> > > Would that be necessary? Is there any need to remap it? Couldn't you > just do the straightforward phys->virt mapping and use the page where it > lies? Catch-22. If the page is not mapped yet you can't use it where it lies. Eric _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
