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Message-ID: <AANLkTimcdVvmhBr6g_Eo0kWX9mdeNmXjd=CBQrvUGm8S@mail.gmail.com>
Date: Mon, 7 Feb 2011 21:16:27 -0800
From: Yinghai Lu <yinghai@...nel.org>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc: "H. Peter Anvin" <hpa@...or.com>,
Jeremy Fitzhardinge <jeremy@...p.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"x86@...nel.org" <x86@...nel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Jan Beulich <JBeulich@...ell.com>
Subject: Re: [PATCH] x86/mm/init: respect memblock reserved regions when
destroying mappings
On Mon, Feb 7, 2011 at 11:00 AM, Stefano Stabellini
<stefano.stabellini@...citrix.com> wrote:
> On Mon, 7 Feb 2011, Stefano Stabellini wrote:
>> On Sun, 6 Feb 2011, Yinghai Lu wrote:
>> > On 02/05/2011 11:30 PM, H. Peter Anvin wrote:
>> > > On 02/05/2011 11:02 PM, Yinghai Lu wrote:
>> > >> why not just move calling cleanup_highmap down?
>> > >>
>> > >> something like attached patch.
>> > >
>> > > This patch looks very clean and looks on the surface of it like it is
>> > > removing some ugly ad hoc code, but (as always) it needs a description
>> > > about the problem it solves and why it is correct.
>> >
>> > Sure.
>> >
>> >
>> > Jeremy and xen guys, can you please check if it works well with xen ?
>> >
>>
>> Actually this patch makes things worse on xen, because before
>> cleanup_highmap() wasn't called at all on xen (on purpose) and now it
>> is, fully destroying all the mappings we have at _end.
>>
>> Can we add a check on memblock reserved regions in cleanup_highmap()?
>
> In case you are wondering how Yinghai Lu's patch would look like with
> the added check, here it is:
>
>
> diff --git a/arch/x86/include/asm/memblock.h b/arch/x86/include/asm/memblock.h
> index 19ae14b..184f778 100644
> --- a/arch/x86/include/asm/memblock.h
> +++ b/arch/x86/include/asm/memblock.h
> @@ -3,6 +3,7 @@
>
> #define ARCH_DISCARD_MEMBLOCK
>
> +bool memblock_check_reserved_size(u64 *addrp, u64 *sizep, u64 align);
> u64 memblock_x86_find_in_range_size(u64 start, u64 *sizep, u64 align);
> void memblock_x86_to_bootmem(u64 start, u64 end);
>
> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
> index 975f709..28686b6 100644
> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -165,7 +165,7 @@ static inline int pgd_large(pgd_t pgd) { return 0; }
> #define __swp_entry_to_pte(x) ((pte_t) { .pte = (x).val })
>
> extern int kern_addr_valid(unsigned long addr);
> -extern void cleanup_highmap(void);
> +extern void cleanup_highmap(unsigned long end);
>
> #define HAVE_ARCH_UNMAPPED_AREA
> #define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
> index 2d2673c..5655c22 100644
> --- a/arch/x86/kernel/head64.c
> +++ b/arch/x86/kernel/head64.c
> @@ -77,9 +77,6 @@ void __init x86_64_start_kernel(char * real_mode_data)
> /* Make NULL pointers segfault */
> zap_identity_mappings();
>
> - /* Cleanup the over mapped high alias */
> - cleanup_highmap();
> -
> max_pfn_mapped = KERNEL_IMAGE_SIZE >> PAGE_SHIFT;
>
> for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index d3cfe26..91afde6 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -297,6 +297,9 @@ static void __init init_gbpages(void)
> static inline void init_gbpages(void)
> {
> }
> +static void __init cleanup_highmap(unsigned long end)
> +{
> +}
> #endif
>
> static void __init reserve_brk(void)
> @@ -922,6 +925,9 @@ void __init setup_arch(char **cmdline_p)
> */
> reserve_brk();
>
> + /* Cleanup the over mapped high alias after _brk_end*/
> + cleanup_highmap(_brk_end);
> +
> memblock.current_limit = get_max_mapped();
> memblock_x86_fill();
>
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 947f42a..f13ff3a 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -279,25 +279,6 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
> load_cr3(swapper_pg_dir);
> #endif
>
> -#ifdef CONFIG_X86_64
> - if (!after_bootmem && !start) {
> - pud_t *pud;
> - pmd_t *pmd;
> -
> - mmu_cr4_features = read_cr4();
> -
> - /*
> - * _brk_end cannot change anymore, but it and _end may be
> - * located on different 2M pages. cleanup_highmap(), however,
> - * can only consider _end when it runs, so destroy any
> - * mappings beyond _brk_end here.
> - */
> - pud = pud_offset(pgd_offset_k(_brk_end), _brk_end);
> - pmd = pmd_offset(pud, _brk_end - 1);
> - while (++pmd <= pmd_offset(pud, (unsigned long)_end - 1))
> - pmd_clear(pmd);
> - }
> -#endif
> __flush_tlb_all();
>
> if (!after_bootmem && e820_table_end > e820_table_start)
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 71a5929..028c49e 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -297,18 +297,26 @@ void __init init_extra_mapping_uc(unsigned long phys, unsigned long size)
> * rounded up to the 2MB boundary. This catches the invalid pmds as
> * well, as they are located before _text:
> */
> -void __init cleanup_highmap(void)
> +void __init cleanup_highmap(unsigned long end)
> {
> unsigned long vaddr = __START_KERNEL_map;
> - unsigned long end = roundup((unsigned long)_end, PMD_SIZE) - 1;
> pmd_t *pmd = level2_kernel_pgt;
> pmd_t *last_pmd = pmd + PTRS_PER_PMD;
> + u64 size, addrp;
> + bool changed;
> +
> + end = roundup(end, PMD_SIZE) - 1;
>
> for (; pmd < last_pmd; pmd++, vaddr += PMD_SIZE) {
> if (pmd_none(*pmd))
> continue;
> - if (vaddr < (unsigned long) _text || vaddr > end)
> - set_pmd(pmd, __pmd(0));
> + if (vaddr < (unsigned long) _text || vaddr > end) {
> + addrp = __pa(vaddr);
> + size = PMD_SIZE;
> + changed = memblock_check_reserved_size(&addrp, &size, PMD_SIZE);
> + if (!changed && size)
> + set_pmd(pmd, __pmd(0));
> + }
for native path, memblock_check_reserved_size() are called 256 times
without obvious reasons.
Yinghai
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