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Background: I've implemented 1K/2K page tables for s390. These sub-page page tables are required to properly support the s390 virtualization instruction with KVM. The SIE instruction requires that the page tables have 256 page table entries (pte) followed by 256 page status table entries (pgste). The pgstes are only required if the process is using the SIE instruction. The pgstes are updated by the hardware and by the hypervisor for a number of reasons, one of them is dirty and reference bit tracking. To avoid wasting memory the standard pte table allocation should return 1K/2K (31/64 bit) and 2K/4K if the process is using SIE. Problem: Page size on s390 is 4K, page table size is 1K or 2K. That means the s390 version for pte_alloc_one cannot return a pointer to a struct page. Trouble is that with the CONFIG_HIGHPTE feature on x86 pte_alloc_one cannot return a pointer to a pte either, since that would require more than 32 bit for the return value of pte_alloc_one (and the pte * would not be accessible since its not kmapped). Solution: The only solution I found to this dilemma is a new typedef: a pgtable_t. For s390 pgtable_t will be a (pte *) - to be introduced with a later patch. For everybody else it will be a (struct page *). The additional problem with the initialization of the ptl lock and the NR_PAGETABLE accounting is solved with a constructor pgtable_page_ctor and a destructor pgtable_page_dtor. The page table allocation and free functions need to call these two whenever a page table page is allocated or freed. pmd_populate will get a pgtable_t instead of a struct page pointer. To get the pgtable_t back from a pmd entry that has been installed with pmd_populate a new function pmd_pgtable is added. It replaces the pmd_page call in free_pte_range and apply_to_pte_range. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
82 lines
2.3 KiB
C
82 lines
2.3 KiB
C
#ifndef _ASM_PAGE_H
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#define _ASM_PAGE_H
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#include <asm/virtconvert.h>
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#include <asm/mem-layout.h>
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#include <asm/sections.h>
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#include <asm/setup.h>
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#ifndef __ASSEMBLY__
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#define get_user_page(vaddr) __get_free_page(GFP_KERNEL)
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#define free_user_page(page, addr) free_page(addr)
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#define clear_page(pgaddr) memset((pgaddr), 0, PAGE_SIZE)
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#define copy_page(to,from) memcpy((to), (from), PAGE_SIZE)
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#define clear_user_page(pgaddr, vaddr, page) memset((pgaddr), 0, PAGE_SIZE)
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#define copy_user_page(vto, vfrom, vaddr, topg) memcpy((vto), (vfrom), PAGE_SIZE)
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/*
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* These are used to make use of C type-checking..
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*/
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typedef struct { unsigned long pte; } pte_t;
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typedef struct { unsigned long ste[64];} pmd_t;
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typedef struct { pmd_t pue[1]; } pud_t;
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typedef struct { pud_t pge[1]; } pgd_t;
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typedef struct { unsigned long pgprot; } pgprot_t;
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typedef struct page *pgtable_t;
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#define pte_val(x) ((x).pte)
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#define pmd_val(x) ((x).ste[0])
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#define pud_val(x) ((x).pue[0])
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#define pgd_val(x) ((x).pge[0])
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#define pgprot_val(x) ((x).pgprot)
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#define __pte(x) ((pte_t) { (x) } )
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#define __pmd(x) ((pmd_t) { (x) } )
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#define __pud(x) ((pud_t) { (x) } )
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#define __pgd(x) ((pgd_t) { (x) } )
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#define __pgprot(x) ((pgprot_t) { (x) } )
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#define PTE_MASK PAGE_MASK
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/* to align the pointer to the (next) page boundary */
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#define PAGE_ALIGN(addr) (((addr) + PAGE_SIZE - 1) & PAGE_MASK)
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#define devmem_is_allowed(pfn) 1
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#define __pa(vaddr) virt_to_phys((void *) (unsigned long) (vaddr))
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#define __va(paddr) phys_to_virt((unsigned long) (paddr))
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#define pfn_to_kaddr(pfn) __va((pfn) << PAGE_SHIFT)
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extern unsigned long max_low_pfn;
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extern unsigned long min_low_pfn;
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extern unsigned long max_pfn;
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#ifdef CONFIG_MMU
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#define pfn_valid(pfn) ((pfn) < max_mapnr)
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#else
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#define ARCH_PFN_OFFSET (PAGE_OFFSET >> PAGE_SHIFT)
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#define pfn_valid(pfn) ((pfn) >= min_low_pfn && (pfn) < max_low_pfn)
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#endif
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#define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
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#define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
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#ifdef CONFIG_MMU
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#define VM_DATA_DEFAULT_FLAGS \
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(VM_READ | VM_WRITE | \
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((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0 ) | \
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VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
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#endif
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#endif /* __ASSEMBLY__ */
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#include <asm-generic/memory_model.h>
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#include <asm-generic/page.h>
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#endif /* _ASM_PAGE_H */
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