On Mon, Oct 08, 2012 at 09:39:11PM -0700, Yinghai Lu wrote:
> Get pgt_buf early from BRK, and use it to map page table at first.
>
> also use the left at first, then use new one.
Left?
>
> -v2: extra xen call back for that new range.
> -v3: fix compiling about #llx in print out that is reported by Fengguang
> -v4: remove the early_pgt_buf_* stuff, because xen interface is ready yet.
> still need to run x86_init.mapping.pagetable_reserve separately.
> so we will waste some pages in BRK, will address that later.
>
> Signed-off-by: Yinghai Lu <ying...@kernel.org>
> ---
> arch/x86/include/asm/pgtable.h | 1 +
> arch/x86/kernel/setup.c | 2 ++
> arch/x86/mm/init.c | 26 +++++++++++++++++++++++++-
> 3 files changed, 28 insertions(+), 1 deletions(-)
>
> 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 0c58f2d..a89f485 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -317,12 +317,22 @@ static void __init find_early_table_space(unsigned long
> start,
> unsigned long good_end,
> unsigned long tables)
> {
> - phys_addr_t base;
> + unsigned long base;
>
> base = memblock_find_in_range(start, good_end, tables, PAGE_SIZE);
> if (!base)
> panic("Cannot find space for the kernel page tables");
>
> + init_memory_mapping(base, base + tables);
> + if (pgt_buf_end > pgt_buf_start) {
> + printk(KERN_DEBUG "kernel direct mapping tables from %#lx to
> %#lx @ [mem %#010lx-%#010lx]\n",
> + base, base + tables - 1, pgt_buf_start << PAGE_SHIFT,
> + (pgt_buf_end << PAGE_SHIFT) - 1);
> +
> + x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start),
> + PFN_PHYS(pgt_buf_end));
> + }
> +
> pgt_buf_start = base >> PAGE_SHIFT;
> pgt_buf_end = pgt_buf_start;
> pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
> @@ -469,6 +479,20 @@ void __init init_mem_mapping(void)
> early_memtest(0, max_pfn_mapped << PAGE_SHIFT);
> }
>
> +RESERVE_BRK(early_pgt_alloc, 16384);
How did you come up with 16KB being the right size? What is this
based on? Can you provide a comment explaining why 16KB is the
right value on 32-bit and 64-bit machines?
> +
> +void __init early_alloc_pgt_buf(void)
> +{
> + unsigned long tables = 16384;
> + phys_addr_t base;
> +
> + base = __pa(extend_brk(tables, PAGE_SIZE));
> +
> + pgt_buf_start = base >> PAGE_SHIFT;
> + pgt_buf_end = pgt_buf_start;
> + pgt_buf_top = pgt_buf_start + (tables >> PAGE_SHIFT);
> +}
> +
> /*
> * devmem_is_allowed() checks to see if /dev/mem access to a certain address
> * is valid. The argument is a physical page number.
> --
> 1.7.7
>
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