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Message-ID: <86802c440806281333t2bede7d0ld54cceda9a1cfb20@mail.gmail.com>
Date: Sat, 28 Jun 2008 13:33:10 -0700
From: "Yinghai Lu" <yhlu.kernel@...il.com>
To: "Jeremy Fitzhardinge" <jeremy@...p.org>
Cc: "Ingo Molnar" <mingo@...e.hu>,
"Thomas Gleixner" <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: fix init_memory_mapping over boundary v2
On Sat, Jun 28, 2008 at 10:38 AM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Yinghai Lu wrote:
>>
>> some end boundary is only page alignment, instead of 2M alignment,
>> so call ker_phycial_mapping_init three times.
>> then don't overmap above the max_low_pfn
>>
>> v2: make init_memory_mapping more solid: start could be any value other
>> than 0
>>
>> Signed-off-by: Yinghai Lu <yhlu.kernel@...il.com>
>>
>> ---
>> arch/x86/mm/init_32.c | 86
>> ++++++++++++++++++++++++++++++++++++--------------
>> 1 file changed, 62 insertions(+), 24 deletions(-)
>>
>> Index: linux-2.6/arch/x86/mm/init_32.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/mm/init_32.c
>> +++ linux-2.6/arch/x86/mm/init_32.c
>> @@ -184,8 +184,9 @@ static inline int is_kernel_text(unsigne
>> * PAGE_OFFSET:
>> */
>> static void __init kernel_physical_mapping_init(pgd_t *pgd_base,
>> - unsigned long start,
>> - unsigned long end)
>> + unsigned long start_pfn,
>> + unsigned long end_pfn,
>> + int use_pse)
>>
>
> Better to use bool for use_pse.
>
>> {
>> int pgd_idx, pmd_idx, pte_ofs;
>> unsigned long pfn;
>> @@ -193,32 +194,30 @@ static void __init kernel_physical_mappi
>> pmd_t *pmd;
>> pte_t *pte;
>> unsigned pages_2m = 0, pages_4k = 0;
>> - unsigned limit_pfn = end >> PAGE_SHIFT;
>> - pgd_idx = pgd_index(PAGE_OFFSET);
>> - pgd = pgd_base + pgd_idx;
>> - pfn = start >> PAGE_SHIFT;
>> + if (!cpu_has_pse)
>> + use_pse = 0;
>>
>
> What are the semantics of the use_pse argument? Is it just a hint? If so,
> then the caller below should just pass a constant 1/true.
>
>> + pfn = start_pfn;
>> + pgd_idx = pgd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
>> + pgd = pgd_base + pgd_idx;
>> for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
>> pmd = one_md_table_init(pgd);
>> - if (pfn >= limit_pfn)
>> +
>> + if (pfn >= end_pfn)
>> continue;
>> - for (pmd_idx = 0;
>> - pmd_idx < PTRS_PER_PMD && pfn < limit_pfn;
>> + pmd_idx = pmd_index((pfn<<PAGE_SHIFT) + PAGE_OFFSET);
>> + pmd += pmd_idx;
>> + for (; pmd_idx < PTRS_PER_PMD && pfn < end_pfn;
>> pmd++, pmd_idx++) {
>> unsigned int addr = pfn * PAGE_SIZE + PAGE_OFFSET;
>> /*
>> * Map with big pages if possible, otherwise
>> * create normal page tables:
>> - *
>> - * Don't use a large page for the first 2/4MB of
>> memory
>> - * because there are often fixed size MTRRs in
>> there
>> - * and overlapping MTRRs into large pages can
>> cause
>> - * slowdowns.
>> */
>> - if (cpu_has_pse && !(pgd_idx == 0 && pmd_idx ==
>> 0)) {
>> + if (use_pse) {
>> unsigned int addr2;
>> pgprot_t prot = PAGE_KERNEL_LARGE;
>> @@ -233,13 +232,12 @@ static void __init kernel_physical_mappi
>> set_pmd(pmd, pfn_pmd(pfn, prot));
>> pfn += PTRS_PER_PTE;
>> - max_pfn_mapped = pfn;
>> continue;
>> }
>> pte = one_page_table_init(pmd);
>> for (pte_ofs = 0;
>> - pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn;
>> + pte_ofs < PTRS_PER_PTE && pfn < end_pfn;
>> pte++, pfn++, pte_ofs++, addr += PAGE_SIZE) {
>> pgprot_t prot = PAGE_KERNEL;
>> @@ -249,7 +247,6 @@ static void __init kernel_physical_mappi
>> pages_4k++;
>> set_pte(pte, pfn_pte(pfn, prot));
>> }
>> - max_pfn_mapped = pfn;
>> }
>> }
>> update_page_count(PG_LEVEL_2M, pages_2m);
>> @@ -729,7 +726,7 @@ void __init setup_bootmem_allocator(void
>> static void __init find_early_table_space(unsigned long end)
>> {
>> - unsigned long puds, pmds, tables, start;
>> + unsigned long puds, pmds, ptes, tables, start;
>> puds = (end + PUD_SIZE - 1) >> PUD_SHIFT;
>> tables = PAGE_ALIGN(puds * sizeof(pud_t));
>> @@ -737,10 +734,15 @@ static void __init find_early_table_spac
>> pmds = (end + PMD_SIZE - 1) >> PMD_SHIFT;
>> tables += PAGE_ALIGN(pmds * sizeof(pmd_t));
>> - if (!cpu_has_pse) {
>> - int ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
>> - tables += PAGE_ALIGN(ptes * sizeof(pte_t));
>> - }
>> + if (cpu_has_pse) {
>> + int extra;
>> + extra = end - ((end>>21) << 21);
>>
>
> That's a bit magic. Isn't that just "extra = end & ((1 << 21) - 1)"? And
> what are you actually computing here anyway?
>
>> + extra += (2<<20);
>>
>
> PMD_SIZE? The comment below says "2/4MB", which corresponds to a
> PAE/non-PAE large PMD.
>
>> + ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
>> + } else
>> + ptes = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
>> +
>> + tables += PAGE_ALIGN(ptes * sizeof(pte_t));
>> /*
>> * RED-PEN putting page tables only on node 0 could
>> @@ -766,6 +768,8 @@ unsigned long __init_refok init_memory_m
>> unsigned long end)
>> {
>> pgd_t *pgd_base = swapper_pg_dir;
>> + unsigned long start_pfn, end_pfn;
>> + unsigned long big_page_start;
>> /*
>> * Find space for the kernel direct mapping tables.
>> @@ -790,7 +794,41 @@ unsigned long __init_refok init_memory_m
>> __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
>> }
>> - kernel_physical_mapping_init(pgd_base, start, end);
>> + /*
>> + * Don't use a large page for the first 2/4MB of memory
>> + * because there are often fixed size MTRRs in there
>> + * and overlapping MTRRs into large pages can cause
>> + * slowdowns.
>> + */
>> + big_page_start = 2UL<<20;
>>
>
> PMD_SIZE again? Non-PAE big pages are 4MB.
thanks, I will try to revive v2...
--
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