From 574c5b3d0e4c0803d3094fd27f83e161345ebe2f Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Fri, 22 Nov 2019 09:25:12 +0100 Subject: mm: Add a vmf_insert_mixed_prot() function MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The TTM module today uses a hack to be able to set a different page protection than struct vm_area_struct::vm_page_prot. To be able to do this properly, add the needed vm functionality as vmf_insert_mixed_prot(). Cc: Andrew Morton Cc: Michal Hocko Cc: "Matthew Wilcox (Oracle)" Cc: "Kirill A. Shutemov" Cc: Ralph Campbell Cc: "Jérôme Glisse" Cc: "Christian König" Signed-off-by: Thomas Hellstrom Acked-by: Christian König Acked-by: Michal Hocko Acked-by: Andrew Morton --- mm/memory.c | 43 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 39 insertions(+), 4 deletions(-) (limited to 'mm/memory.c') diff --git a/mm/memory.c b/mm/memory.c index 606da187d1de..f5e1fe1d5331 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1664,6 +1664,9 @@ out_unlock: * vmf_insert_pfn_prot should only be used if using multiple VMAs is * impractical. * + * See vmf_insert_mixed_prot() for a discussion of the implication of using + * a value of @pgprot different from that of @vma->vm_page_prot. + * * Context: Process context. May allocate using %GFP_KERNEL. * Return: vm_fault_t value. */ @@ -1737,9 +1740,9 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn) } static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, - unsigned long addr, pfn_t pfn, bool mkwrite) + unsigned long addr, pfn_t pfn, pgprot_t pgprot, + bool mkwrite) { - pgprot_t pgprot = vma->vm_page_prot; int err; BUG_ON(!vm_mixed_ok(vma, pfn)); @@ -1782,10 +1785,42 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma, return VM_FAULT_NOPAGE; } +/** + * vmf_insert_mixed_prot - insert single pfn into user vma with specified pgprot + * @vma: user vma to map to + * @addr: target user address of this page + * @pfn: source kernel pfn + * @pgprot: pgprot flags for the inserted page + * + * This is exactly like vmf_insert_mixed(), except that it allows drivers to + * to override pgprot on a per-page basis. + * + * Typically this function should be used by drivers to set caching- and + * encryption bits different than those of @vma->vm_page_prot, because + * the caching- or encryption mode may not be known at mmap() time. + * This is ok as long as @vma->vm_page_prot is not used by the core vm + * to set caching and encryption bits for those vmas (except for COW pages). + * This is ensured by core vm only modifying these page table entries using + * functions that don't touch caching- or encryption bits, using pte_modify() + * if needed. (See for example mprotect()). + * Also when new page-table entries are created, this is only done using the + * fault() callback, and never using the value of vma->vm_page_prot, + * except for page-table entries that point to anonymous pages as the result + * of COW. + * + * Context: Process context. May allocate using %GFP_KERNEL. + * Return: vm_fault_t value. + */ +vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr, + pfn_t pfn, pgprot_t pgprot) +{ + return __vm_insert_mixed(vma, addr, pfn, pgprot, false); +} + vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr, pfn_t pfn) { - return __vm_insert_mixed(vma, addr, pfn, false); + return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, false); } EXPORT_SYMBOL(vmf_insert_mixed); @@ -1797,7 +1832,7 @@ EXPORT_SYMBOL(vmf_insert_mixed); vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, pfn_t pfn) { - return __vm_insert_mixed(vma, addr, pfn, true); + return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, true); } EXPORT_SYMBOL(vmf_insert_mixed_mkwrite); -- cgit v1.2.3-59-g8ed1b