Le 05/12/2021 à 17:42, Maxime Bizon a écrit : > > > On Saturday 04 Dec 2021 à 17:42:44 (+0000), Christophe Leroy wrote: > >> I guess all the guard is in the comment ... >> >> /* >> * Set up one of the I/D BAT (block address translation) register pairs. >> * The parameters are not checked; in particular size must be a power >> * of 2 between 128k and 256M. >> */ > > It's missing the aligment rule you just taught me, but it's arguably > not the right place to teach ppc 101.
Indeed > >> Not sure it is that simple. >> >> I'm cooking a patch reusing the block_size() function in mm/book3s32/mmu.c > > Indeed it will handle cases that need more than 2 BATs. Yes, that's the idea. > > Also when mem=2G, I have physical memory mapped twice: > > CONFIG_PAGE_OFFSET=0x80000000 > CONFIG_LOWMEM_SIZE=0x60000000 > > 0: 0x80000000-0x8fffffff 0x00000000 256M Kernel rw m > 1: 0x90000000-0x9fffffff 0x10000000 256M Kernel rw m > 2: 0xa0000000-0xafffffff 0x20000000 256M Kernel rw m > 3: 0xb0000000-0xbfffffff 0x30000000 256M Kernel rw m > 4: 0xc0000000-0xcfffffff 0x40000000 256M Kernel rw m > 5: 0xd0000000-0xdfffffff 0x50000000 256M Kernel rw m > 6: 0xf0000000-0xf7ffffff 0x50000000 128M Kernel rw m > > BAT5 comes from __mmu_mapin_ram(), BAT6 from kasan init > > Is BAT5 needed here ? Sure it is, because that's were kernel expects lowmem to be mapped. Allthough the kernel will unlikely access the 128M reserved for KASAN directly, the other 128M are still needed. > > > Last one, with KASAN and the following layout, I have an non working > kernel with VMALLOC_START > VMALLOC_END: > > mem=2G > CONFIG_PAGE_OFFSET=0x80000000 > CONFIG_LOWMEM_SIZE=0x70000000 > > [ 0.000000] * 0xf0000000..0xfe000000 : kasan shadow mem > [ 0.000000] * 0xef7ff000..0xeffff000 : fixmap > [ 0.000000] * 0xf1000000..0xef7ff000 : vmalloc & ioremap > > > IIUC the safeguard is here: > > arch/powerpc/mm/init_32.c: > /* The amount of lowmem must be within 0xF0000000 - KERNELBASE. */ > #if (CONFIG_LOWMEM_SIZE > (0xF0000000 - PAGE_OFFSET)) > #error "You must adjust CONFIG_LOWMEM_SIZE or CONFIG_KERNEL_START" > > > but the definition needs to be adapted for KASAN=y and require 256 > more MB. > > Hum.. Good point. Christophe
