From ee4f2ea48674b6c9d91bc854edc51a3e6a7168c4 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Thu, 12 Apr 2007 15:30:22 +1000 Subject: [POWERPC] Fix 32-bit mm operations when not using BATs On hash table based 32 bits powerpc's, the hash management code runs with a big spinlock. It's thus important that it never causes itself a hash fault. That code is generally safe (it does memory accesses in real mode among other things) with the exception of the actual access to the code itself. That is, the kernel text needs to be accessible without taking a hash miss exceptions. This is currently guaranteed by having a BAT register mapping part of the linear mapping permanently, which includes the kernel text. But this is not true if using the "nobats" kernel command line option (which can be useful for debugging) and will not be true when using DEBUG_PAGEALLOC implemented in a subsequent patch. This patch fixes this by pre-faulting in the hash table pages that hit the kernel text, and making sure we never evict such a page under hash pressure. Signed-off-by: Benjamin Herrenchmidt arch/powerpc/mm/hash_low_32.S | 22 ++++++++++++++++++++-- arch/powerpc/mm/mem.c | 3 --- arch/powerpc/mm/mmu_decl.h | 4 ++++ arch/powerpc/mm/pgtable_32.c | 11 +++++++---- 4 files changed, 31 insertions(+), 9 deletions(-) Signed-off-by: Paul Mackerras --- arch/powerpc/mm/pgtable_32.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'arch/powerpc/mm/pgtable_32.c') diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c index 95d3afe36b5..f75f2fc7bc7 100644 --- a/arch/powerpc/mm/pgtable_32.c +++ b/arch/powerpc/mm/pgtable_32.c @@ -282,16 +282,19 @@ int map_page(unsigned long va, phys_addr_t pa, int flags) void __init mapin_ram(void) { unsigned long v, p, s, f; + int ktext; s = mmu_mapin_ram(); v = KERNELBASE + s; p = PPC_MEMSTART + s; for (; s < total_lowmem; s += PAGE_SIZE) { - if ((char *) v >= _stext && (char *) v < etext) - f = _PAGE_RAM_TEXT; - else - f = _PAGE_RAM; + ktext = ((char *) v >= _stext && (char *) v < etext); + f = ktext ?_PAGE_RAM_TEXT : _PAGE_RAM; map_page(v, p, f); +#ifdef CONFIG_PPC_STD_MMU_32 + if (ktext) + hash_preload(&init_mm, v, 0, 0x300); +#endif v += PAGE_SIZE; p += PAGE_SIZE; } -- cgit v1.2.3-70-g09d2