On Sat, 6 Oct 2012, Yinghai Lu wrote: > set pgt_buf early from BRK, and use it to map page table at first. > > also use the left at first, then use new extend one. > > -v2: extra xen call back for that new range. > > Signed-off-by: Yinghai Lu <ying...@kernel.org> > --- > arch/x86/include/asm/init.h | 4 ++++ > arch/x86/include/asm/pgtable.h | 1 + > arch/x86/kernel/setup.c | 2 ++ > arch/x86/mm/init.c | 25 +++++++++++++++++++++++++ > arch/x86/mm/init_32.c | 8 ++++++-- > arch/x86/mm/init_64.c | 8 ++++++-- > 6 files changed, 44 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h > index 4f13998..2f32eea 100644 > --- a/arch/x86/include/asm/init.h > +++ b/arch/x86/include/asm/init.h > @@ -16,4 +16,8 @@ extern unsigned long __initdata pgt_buf_start; > extern unsigned long __meminitdata pgt_buf_end; > extern unsigned long __meminitdata pgt_buf_top; > > +extern unsigned long __initdata early_pgt_buf_start; > +extern unsigned long __meminitdata early_pgt_buf_end; > +extern unsigned long __meminitdata early_pgt_buf_top; > + > #endif /* _ASM_X86_INIT_32_H */ > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 52d40a1..25fa5bb 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -599,6 +599,7 @@ static inline int pgd_none(pgd_t pgd) > > extern int direct_gbpages; > void init_mem_mapping(void); > +void early_alloc_pgt_buf(void); > > /* local pte updates need not use xchg for locking */ > static inline pte_t native_local_ptep_get_and_clear(pte_t *ptep) > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 4989f80..7eb6855 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -896,6 +896,8 @@ void __init setup_arch(char **cmdline_p) > > reserve_ibft_region(); > > + early_alloc_pgt_buf(); > + > /* > * Need to conclude brk, before memblock_x86_fill() > * it could use memblock_find_in_range, could overlap with > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index cf662ba..c32eed1 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -21,6 +21,10 @@ unsigned long __initdata pgt_buf_start; > unsigned long __meminitdata pgt_buf_end; > unsigned long __meminitdata pgt_buf_top; > > +unsigned long __initdata early_pgt_buf_start; > +unsigned long __meminitdata early_pgt_buf_end; > +unsigned long __meminitdata early_pgt_buf_top; > + > int after_bootmem; > > int direct_gbpages > @@ -291,6 +295,11 @@ static void __init find_early_table_space(unsigned long > start, > if (!base) > panic("Cannot find space for the kernel page tables"); > > + init_memory_mapping(base, base + tables); > + printk(KERN_DEBUG "kernel direct mapping tables from %#llx to %#llx @ > [mem %#010lx-%#010lx]\n", > + base, base + tables - 1, early_pgt_buf_start << PAGE_SHIFT, > + (early_pgt_buf_end << PAGE_SHIFT) - 1); > + > pgt_buf_start = base >> PAGE_SHIFT; > pgt_buf_end = pgt_buf_start; > pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT); > @@ -430,6 +439,8 @@ void __init init_mem_mapping(void) > x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start), > PFN_PHYS(pgt_buf_end)); > } > + x86_init.mapping.pagetable_reserve(PFN_PHYS(early_pgt_buf_start), > + PFN_PHYS(early_pgt_buf_end));
pagetable_reserve is not the right hook: pagetable_reserve tells the subsystem that the memory range you are passing is going to be used for pagetable pages. It is used to reserve that range using memblock_reserve. On Xen is also used to mark RW any pages _outside_ that range that have been marked RO: implicitely we assume that the full range is pgt_buf_start-pgt_buf_top and we mark it RO (see Xen memory contraints on pagetable pages, as decribed by Konrad). Calling pagetable_reserve(real_start, real_end) reserves real_start-real_end as pagetable pages and frees pgt_buf_start-real_start and real_end-pgt_buf_top. So the problem is that at the moment we don't have a hook to say: "the range of pagetable pages is pgt_buf_start-pgt_buf_top". In fact if you give a look at arch/x86/xen/mmu.c you'll find few references to pgt_buf_start, pgt_buf_end, pgt_buf_top, that shouldn't really be there. -- 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/