path: root/mm/memory.c
diff options
authorThomas Hellstrom <thellstrom@vmware.com>2019-11-22 09:25:12 +0100
committerThomas Hellstrom <thellstrom@vmware.com>2020-01-16 10:32:33 +0100
commit574c5b3d0e4c0803d3094fd27f83e161345ebe2f (patch)
tree5b75b8932101bbe6886192d918709cc8ae219fdb /mm/memory.c
parentMerge tag 'drm-intel-next-2020-01-14' of git://anongit.freedesktop.org/drm/drm-intel into drm-next (diff)
mm: Add a vmf_insert_mixed_prot() function
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 <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: "Christian König" <christian.koenig@amd.com> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Christian König <christian.koenig@amd.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to '')
1 files changed, 39 insertions, 4 deletions
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,
+ * 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);
@@ -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);