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Date: Mon, 16 Mar 2009 12:48:55 -0700 From: Yinghai Lu <yinghai@...nel.org> To: Jeremy Fitzhardinge <jeremy@...p.org> CC: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [crash] Re: Latest brk patchset Jeremy Fitzhardinge wrote: > H. Peter Anvin wrote: >> Jeremy Fitzhardinge wrote: >>> Yinghai Lu wrote: >>>> could be max_pfn_mapped change in head_32.S that reduce mapping >>>> range to _end only. >>>> >>> >>> Yes, I would say you're right. Trimming the mapping to _end only >>> leaves the space under the kernel avaliable for allocating pagetable >>> from e820 space. In this case we've got DEBUG_PAGEALLOC enabled, >>> which inhibits the use of PSE, and BIOS corruption checking on, which >>> eats a chunk of low memory. In combination, there's only 0x8f000 >>> bytes free below the kernel, and it needs 0xe1000 to allocate for >>> pagetables. >>> >>> Reverting 2bd2753ff46346543ab92e80df9d96366e21baa5 fixes the problem >>> for me, though it does result in a kernel with a 73MB BSS... >>> >> >> Waitaminute... there is no way we could end up with 73 MB page tables >> unless something is seriously screwy. Even with PAE and !PSE, we only >> get 2 MB worth of page tables for each 1 GB mapped -- even with a 4:4 >> scheme this is only 8 MB. > > Yes, something odd happened there. > > Anyway, this patch fixes it. I also removed ALLOCATOR_SLOP, because it > is left over from when we used the bootmem allocator for the linear > mapping pagetable, before using e820 allocation. > > Did you also want to pull the changes to put the brk in .brk and rename > the reservation symbols? > > J > > The following changes since commit > 2bd2753ff46346543ab92e80df9d96366e21baa5: > Yinghai Lu (1): > x86: put initial_pg_tables into .bss > > are available in the git repository at: > > ssh://master.kernel.org/~jeremy/git/xen.git tip/x86/setup-memory > > Jeremy Fitzhardinge (2): > x86-32: make sure we map enough to fit linear map pagetables > x86-32: remove ALLOCATOR_SLOP from head_32.S > > arch/x86/kernel/head_32.S | 32 ++++++++++++++++++++------------ > 1 files changed, 20 insertions(+), 12 deletions(-) > >> From 378c46828de3f34d94d83f08b2d6d81a0fc8f108 Mon Sep 17 00:00:00 2001 > From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com> > Date: Mon, 16 Mar 2009 12:07:54 -0700 > Subject: [PATCH] x86-32: make sure we map enough to fit linear map > pagetables > > head_32.S needs to map the kernel itself, and enough space so > that mm/init.c can allocate space from the e820 allocator > for the linear map of low memory. > > Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com> > > diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S > index c79741c..e929619 100644 > --- a/arch/x86/kernel/head_32.S > +++ b/arch/x86/kernel/head_32.S > @@ -38,8 +38,8 @@ > #define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id > > /* > - * This is how much memory *in addition to the memory covered up to > - * and including _end* we need mapped initially. > + * This is how much memory in addition to the memory covered up to > + * and including _end we need mapped initially. > * We need: > * (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE) > * (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE) > @@ -52,19 +52,28 @@ > * KERNEL_IMAGE_SIZE should be greater than pa(_end) > * and small than max_low_pfn, otherwise will waste some page table entries > */ > -LOW_PAGES = (KERNEL_IMAGE_SIZE + PAGE_SIZE_asm - 1)>>PAGE_SHIFT > > #if PTRS_PER_PMD > 1 > -PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD > +#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD) > #else > -PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD) > +#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD) > #endif > ALLOCATOR_SLOP = 4 > > -INIT_MAP_SIZE = (PAGE_TABLE_SIZE + ALLOCATOR_SLOP) * PAGE_SIZE_asm > -RESERVE_BRK(pagetables, INIT_MAP_SIZE) > +/* Enough space to fit pagetables for the low memory linear map */ > +MAPPING_BEYOND_END = (PAGE_TABLE_SIZE(1 << (32 - PAGE_SHIFT)) * PAGE_SIZE) that is for 4g? YH > > /* > + * Worst-case size of the kernel mapping we need to make: > + * the worst-case size of the kernel itself, plus the extra we need > + * to map for the linear map. > + */ > +KERNEL_PAGES = (KERNEL_IMAGE_SIZE + MAPPING_BEYOND_END)>>PAGE_SHIFT > + > +INIT_MAP_SIZE = (PAGE_TABLE_SIZE(KERNEL_PAGES) + ALLOCATOR_SLOP) * > PAGE_SIZE_asm > +RESERVE_BRK(pagetables, INIT_MAP_SIZE) > + > +/* > * 32-bit kernel entrypoint; only used by the boot CPU. On entry, > * %esi points to the real-mode code as a 32-bit pointer. > * CS and DS must be 4 GB flat segments, but we don't depend on > @@ -197,9 +206,9 @@ default_entry: > loop 11b > > /* > - * End condition: we must map up to the end. > + * End condition: we must map up to the end + MAPPING_BEYOND_END. > */ > - movl $pa(_end) + PTE_IDENT_ATTR, %ebp > + movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp > cmpl %ebp,%eax > jb 10b > 1: > @@ -229,9 +238,9 @@ page_pde_offset = (__PAGE_OFFSET >> 20); > addl $0x1000,%eax > loop 11b > /* > - * End condition: we must map up to end > + * End condition: we must map up to the end + MAPPING_BEYOND_END. > */ > - movl $pa(_end) + PTE_IDENT_ATTR, %ebp > + movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp > cmpl %ebp,%eax > jb 10b > addl $__PAGE_OFFSET, %edi > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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