mm, dax: introduce pfn_t_special()
In support of removing the VM_MIXEDMAP indication from DAX VMAs, introduce pfn_t_special() for drivers to indicate that _PAGE_SPECIAL should be used for DAX ptes. This also helps identify drivers like dccssblk that only want to use DAX in a read-only fashion without get_user_pages() support. Ideally we could delete axonram and dcssblk DAX support, but if we need to keep it better make it explicit that axonram and dcssblk only support a sub-set of DAX due to missing _PAGE_DEVMAP support. Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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@ -151,7 +151,7 @@ __axon_ram_direct_access(struct axon_ram_bank *bank, pgoff_t pgoff, long nr_page
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resource_size_t offset = pgoff * PAGE_SIZE;
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*kaddr = (void *) bank->io_addr + offset;
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*pfn = phys_to_pfn_t(bank->ph_addr + offset, PFN_DEV);
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*pfn = phys_to_pfn_t(bank->ph_addr + offset, PFN_DEV|PFN_SPECIAL);
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return (bank->size - offset) / PAGE_SIZE;
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}
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@ -916,7 +916,8 @@ __dcssblk_direct_access(struct dcssblk_dev_info *dev_info, pgoff_t pgoff,
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dev_sz = dev_info->end - dev_info->start + 1;
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*kaddr = (void *) dev_info->start + offset;
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*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset), PFN_DEV);
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*pfn = __pfn_to_pfn_t(PFN_DOWN(dev_info->start + offset),
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PFN_DEV|PFN_SPECIAL);
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return (dev_sz - offset) / PAGE_SIZE;
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}
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@ -15,8 +15,10 @@
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#define PFN_SG_LAST (1ULL << (BITS_PER_LONG_LONG - 2))
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#define PFN_DEV (1ULL << (BITS_PER_LONG_LONG - 3))
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#define PFN_MAP (1ULL << (BITS_PER_LONG_LONG - 4))
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#define PFN_SPECIAL (1ULL << (BITS_PER_LONG_LONG - 5))
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#define PFN_FLAGS_TRACE \
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{ PFN_SPECIAL, "SPECIAL" }, \
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{ PFN_SG_CHAIN, "SG_CHAIN" }, \
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{ PFN_SG_LAST, "SG_LAST" }, \
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{ PFN_DEV, "DEV" }, \
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@ -120,4 +122,15 @@ pud_t pud_mkdevmap(pud_t pud);
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#endif
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#endif /* __HAVE_ARCH_PTE_DEVMAP */
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#ifdef __HAVE_ARCH_PTE_SPECIAL
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static inline bool pfn_t_special(pfn_t pfn)
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{
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return (pfn.val & PFN_SPECIAL) == PFN_SPECIAL;
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}
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#else
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static inline bool pfn_t_special(pfn_t pfn)
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{
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return false;
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}
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#endif /* __HAVE_ARCH_PTE_SPECIAL */
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#endif /* _LINUX_PFN_T_H_ */
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16
mm/memory.c
16
mm/memory.c
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@ -1897,12 +1897,26 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
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}
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EXPORT_SYMBOL(vm_insert_pfn_prot);
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static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
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{
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/* these checks mirror the abort conditions in vm_normal_page */
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if (vma->vm_flags & VM_MIXEDMAP)
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return true;
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if (pfn_t_devmap(pfn))
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return true;
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if (pfn_t_special(pfn))
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return true;
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if (is_zero_pfn(pfn_t_to_pfn(pfn)))
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return true;
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return false;
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}
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static int __vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
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pfn_t pfn, bool mkwrite)
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{
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pgprot_t pgprot = vma->vm_page_prot;
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BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
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BUG_ON(!vm_mixed_ok(vma, pfn));
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if (addr < vma->vm_start || addr >= vma->vm_end)
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return -EFAULT;
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