Messages in this thread Patch in this message | | | Date | Wed, 2 Mar 2011 15:23:48 +0000 | From | Stefano Stabellini <> | Subject | Re: "x86-64, mm: Put early page table high" causes crash on Xen |
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On Tue, 1 Mar 2011, Yinghai Lu wrote: > We do need map_low_page ( BTW, that name is totally misleading...) > > the reason is we put page_table high and at that time is not under max_pfn_mapped. (aka not mapped). > > So have to use > adr = early_memremap(phys & PAGE_MASK, PAGE_SIZE); > to early map it and Read/Write to it.
I think I have figured out a way to update the logic of mask_rw_pte to account for the new way of allocating kernel pagetables. The appended patch fix the boot crash for me.
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xen: update mask_rw_pte after kernel page tables init changes
Already existing kernel page table pages can now be mapped using early_ioremap too so we need to update mask_rw_pte to make sure these pages are still mapped RO. We do that by mapping RO all the pages mapped using early_ioremap apart from the last one that has been allocated because it is not a page table page yet (it has been hooked into the page tables yet).
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 62192cd..2ff68be 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1440,10 +1440,12 @@ static __init pte_t mask_rw_pte(pte_t *ptep, pte_t pte) /* * If the new pfn is within the range of the newly allocated * kernel pagetable, and it isn't being mapped into an - * early_ioremap fixmap slot, make sure it is RO. + * early_ioremap fixmap slot as a freshly allocated page, make sure + * it is RO. */ - if (!is_early_ioremap_ptep(ptep) && - pfn >= pgt_buf_start && pfn < pgt_buf_end) + if (((!is_early_ioremap_ptep(ptep) && + pfn >= pgt_buf_start && pfn < pgt_buf_end)) || + (is_early_ioremap_ptep(ptep) && pfn != (pgt_buf_end - 1))) pte = pte_wrprotect(pte); return pte;
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