On Thu, Aug 30, 2018 at 03:25:42PM +0200, Thomas Gleixner wrote: > On Thu, 30 Aug 2018, Feng Tang wrote: > > On Thu, Aug 30, 2018 at 03:05:31PM +0200, Thomas Gleixner wrote: > > > > Those [_text, __bss_stop] is not able to be used by alloc_bootmem(). > > > > And I > > > > only got this patch, and really appreciate any good suggestions. > > > > > > And why do you want to use bootmem in the first place? If boot mem is > > > going > > > away, why are you not fixing the early console crap to NOT use bootmem at > > > all? > > > > The earlycon need use fixmap to map the mmio register, while fixmap will > > need a new page for page table if the pmd/pte is not already their, as shown > > in the commit log: > > > > panic+0xd2/0x220 > > __alloc_bootmem+0x31/0x34 > > spp_getpage+0x60/0x8a > > fill_pte+0x71/0x130 > > __set_pte_vaddr+0x1d/0x50 > > set_pte_vaddr+0x3c/0x60 > > __native_set_fixmap+0x23/0x30 > > native_set_fixmap+0x30/0x40 > > setup_earlycon+0x1e0/0x32f > > param_setup_earlycon+0x13/0x22 > > do_early_param+0x5b/0x90 > > parse_args+0x1f7/0x300 > > parse_early_options+0x24/0x28 > > parse_early_param+0x65/0x73 > > setup_arch+0x31e/0x9f1 > > start_kernel+0x58/0x44e > > > > inside the spp_getpage(): > > > > if (after_bootmem) > > ptr = (void *) get_zeroed_page(GFP_ATOMIC); > > else > > ptr = alloc_bootmem_pages(PAGE_SIZE); > > And where is the problem? We know that we need the fixmap during early boot > anyway, so allocating the PTE page statically and setting it up early > enough is not really rocket science. No allocator required.
Yes, if the bootmem itslef is going way, setting up the page table for fixmap is a cleaner solution. Thanks, Feng
