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authorDave Airlie <airlied@redhat.com>2020-01-31 15:18:21 +1000
committerDave Airlie <airlied@redhat.com>2020-01-31 16:58:35 +1000
commitb45f1b3b585e195a7daead16d914e164310b1df6 (patch)
tree6559d233ad438a3ac7ca2f9092c671284a6a9512 /mm
parentMerge branch 'linux-5.6' of git://github.com/skeggsb/linux into drm-next (diff)
parentmm, drm/ttm: Fix vm page protection handling (diff)
downloadlinux-dev-b45f1b3b585e195a7daead16d914e164310b1df6.tar.xz
linux-dev-b45f1b3b585e195a7daead16d914e164310b1df6.zip
Merge branch 'ttm-prot-fix' of git://people.freedesktop.org/~thomash/linux into drm-next
A small fix for the long-standing ttm vm page protection hack. Sent as a separate PR as it touches mm, has all acks in place. Signed-off-by: Dave Airlie <airlied@redhat.com> From: Thomas Hellström (VMware) <thellstrom@vmware.com> Link: https://patchwork.freedesktop.org/patch/msgid/20200116102411.3056-1-thomas_os@shipmail.org
Diffstat (limited to 'mm')
-rw-r--r--mm/memory.c44
1 files changed, 40 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c
index 45442d9a4f52..e24c7d22b117 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 +1785,43 @@ 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);
+}
+EXPORT_SYMBOL(vmf_insert_mixed_prot);
+
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 +1833,7 @@ 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);