+ mm-add-definition-of-pmd_page_order.patch added to -mm tree

* + mm-add-definition-of-pmd_page_order.patch added to -mm tree
@ 2020-11-12 22:13 akpm
  0 siblings, 0 replies; 10+ messages in thread
From: akpm @ 2020-11-12 22:13 UTC (permalink / raw)
  To: arnd, bp, catalin.marinas, cl, dan.j.williams, dave.hansen,
	david, elena.reshetova, hagen, hpa, jejb, kirill, luto,
	mark.rutland, mingo, mm-commits, mtk.manpages, palmerdabbelt,
	paul.walmsley, peterz, rick.p.edgecombe, rppt, shuah, tglx,
	tycho, viro, will, willy


The patch titled
     Subject: mm: add definition of PMD_PAGE_ORDER
has been added to the -mm tree.  Its filename is
     mm-add-definition-of-pmd_page_order.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-add-definition-of-pmd_page_order.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-add-definition-of-pmd_page_order.patch

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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there every 3-4 working days

------------------------------------------------------
From: Mike Rapoport <rppt@linux.ibm.com>
Subject: mm: add definition of PMD_PAGE_ORDER

Patch series "mm: introduce memfd_secret system call to create "secret" memory areas", v8.

This is an implementation of "secret" mappings backed by a file
descriptor.

The file descriptor backing secret memory mappings is created using a
dedicated memfd_secret system call The desired protection mode for the
memory is configured using flags parameter of the system call.  The mmap()
of the file descriptor created with memfd_secret() will create a "secret"
memory mapping.  The pages in that mapping will be marked as not present
in the direct map and will have desired protection bits set in the user
page table.  For instance, current implementation allows uncached
mappings.

Although normally Linux userspace mappings are protected from other users,
such secret mappings are useful for environments where a hostile tenant is
trying to trick the kernel into giving them access to other tenants
mappings.

Additionally, in the future the secret mappings may be used as a mean to
protect guest memory in a virtual machine host.

For demonstration of secret memory usage we've created a userspace library

https://git.kernel.org/pub/scm/linux/kernel/git/jejb/secret-memory-preloader.git

that does two things: the first is act as a preloader for openssl to
redirect all the OPENSSL_malloc calls to secret memory meaning any secret
keys get automatically protected this way and the other thing it does is
expose the API to the user who needs it.  We anticipate that a lot of the
use cases would be like the openssl one: many toolkits that deal with
secret keys already have special handling for the memory to try to give
them greater protection, so this would simply be pluggable into the
toolkits without any need for user application modification.

Hiding secret memory mappings behind an anonymous file allows (ab)use of
the page cache for tracking pages allocated for the "secret" mappings as
well as using address_space_operations for e.g.  page migration callbacks.

The anonymous file may be also used implicitly, like hugetlb files, to
implement mmap(MAP_SECRET) and use the secret memory areas with "native"
mm ABIs in the future.

To limit fragmentation of the direct map to splitting only PUD-size pages,
I've added an amortizing cache of PMD-size pages to each file descriptor
that is used as an allocation pool for the secret memory areas.

As the memory allocated by secretmem becomes unmovable, we use CMA to back
large page caches so that page allocator won't be surprised by failing
attempt to migrate these pages.


This patch (of 9):

The definition of PMD_PAGE_ORDER denoting the number of base pages in the
second-level leaf page is already used by DAX and maybe handy in other
cases as well.

Several architectures already have definition of PMD_ORDER as the size of
second level page table, so to avoid conflict with these definitions use
PMD_PAGE_ORDER name and update DAX respectively.

Link: https://lkml.kernel.org/r/20201110151444.20662-2-rppt@kernel.org
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/dax.c                |   11 ++++-------
 include/linux/pgtable.h |    3 +++
 2 files changed, 7 insertions(+), 7 deletions(-)

--- a/fs/dax.c~mm-add-definition-of-pmd_page_order
+++ a/fs/dax.c
@@ -49,9 +49,6 @@ static inline unsigned int pe_order(enum
 #define PG_PMD_COLOUR	((PMD_SIZE >> PAGE_SHIFT) - 1)
 #define PG_PMD_NR	(PMD_SIZE >> PAGE_SHIFT)
 
-/* The order of a PMD entry */
-#define PMD_ORDER	(PMD_SHIFT - PAGE_SHIFT)
-
 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
 static int __init init_dax_wait_table(void)
@@ -98,7 +95,7 @@ static bool dax_is_locked(void *entry)
 static unsigned int dax_entry_order(void *entry)
 {
 	if (xa_to_value(entry) & DAX_PMD)
-		return PMD_ORDER;
+		return PMD_PAGE_ORDER;
 	return 0;
 }
 
@@ -1470,7 +1467,7 @@ static vm_fault_t dax_iomap_pmd_fault(st
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct address_space *mapping = vma->vm_file->f_mapping;
-	XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_ORDER);
+	XA_STATE_ORDER(xas, &mapping->i_pages, vmf->pgoff, PMD_PAGE_ORDER);
 	unsigned long pmd_addr = vmf->address & PMD_MASK;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 	bool sync;
@@ -1529,7 +1526,7 @@ static vm_fault_t dax_iomap_pmd_fault(st
 	 * entry is already in the array, for instance), it will return
 	 * VM_FAULT_FALLBACK.
 	 */
-	entry = grab_mapping_entry(&xas, mapping, PMD_ORDER);
+	entry = grab_mapping_entry(&xas, mapping, PMD_PAGE_ORDER);
 	if (xa_is_internal(entry)) {
 		result = xa_to_internal(entry);
 		goto fallback;
@@ -1695,7 +1692,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *
 	if (order == 0)
 		ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
 #ifdef CONFIG_FS_DAX_PMD
-	else if (order == PMD_ORDER)
+	else if (order == PMD_PAGE_ORDER)
 		ret = vmf_insert_pfn_pmd(vmf, pfn, FAULT_FLAG_WRITE);
 #endif
 	else
--- a/include/linux/pgtable.h~mm-add-definition-of-pmd_page_order
+++ a/include/linux/pgtable.h
@@ -28,6 +28,9 @@
 #define USER_PGTABLES_CEILING	0UL
 #endif
 
+/* Number of base pages in a second level leaf page */
+#define PMD_PAGE_ORDER	(PMD_SHIFT - PAGE_SHIFT)
+
 /*
  * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
  *
_

Patches currently in -mm which might be from rppt@linux.ibm.com are

alpha-switch-from-discontigmem-to-sparsemem.patch
ia64-remove-custom-__early_pfn_to_nid.patch
ia64-remove-ifdef-config_zone_dma32-statements.patch
ia64-discontig-paging_init-remove-local-max_pfn-calculation.patch
ia64-split-virtual-map-initialization-out-of-paging_init.patch
ia64-forbid-using-virtual_mem_map-with-flatmem.patch
ia64-make-sparsemem-default-and-disable-discontigmem.patch
arm-remove-config_arch_has_holes_memorymodel.patch
arm-arm64-move-free_unused_memmap-to-generic-mm.patch
arc-use-flatmem-with-freeing-of-unused-memory-map-instead-of-discontigmem.patch
m68k-mm-make-node-data-and-node-setup-depend-on-config_discontigmem.patch
m68k-mm-enable-use-of-generic-memory_modelh-for-discontigmem.patch
m68k-deprecate-discontigmem.patch
mm-introduce-debug_pagealloc_mapunmap_pages-helpers.patch
pm-hibernate-make-direct-map-manipulations-more-explicit.patch
arch-mm-restore-dependency-of-__kernel_map_pages-on-debug_pagealloc.patch
arch-mm-make-kernel_page_present-always-available.patch
mm-add-definition-of-pmd_page_order.patch
mmap-make-mlock_future_check-global.patch
set_memory-allow-set_direct_map__noflush-for-multiple-pages.patch
mm-introduce-memfd_secret-system-call-to-create-secret-memory-areas.patch
secretmem-use-pmd-size-pages-to-amortize-direct-map-fragmentation.patch
secretmem-add-memcg-accounting.patch
pm-hibernate-disable-when-there-are-active-secretmem-users.patch
arch-mm-wire-up-memfd_secret-system-call-were-relevant.patch
secretmem-test-add-basic-selftest-for-memfd_secret2.patch


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