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authorMike Rapoport <rppt@linux.ibm.com>2020-12-10 15:42:21 +1100
committerStephen Rothwell <sfr@canb.auug.org.au>2020-12-16 18:03:06 +1100
commit067806a2efd3751df198164ca693d45d23e2fb41 (patch)
treee8c2b9ab02bfaef1b7aa68f11422a11bb33c8656
parent694a3cbbfd6d8c73f8dc7d1da5068d141ccb2ce0 (diff)
downloadlinux-067806a2efd3751df198164ca693d45d23e2fb41.tar.gz
secretmem: use PMD-size pages to amortize direct map fragmentation
Removing a PAGE_SIZE page from the direct map every time such page is allocated for a secret memory mapping will cause severe fragmentation of the direct map. This fragmentation can be reduced by using PMD-size pages as a pool for small pages for secret memory mappings. Add a gen_pool per secretmem inode and lazily populate this pool with PMD-size pages. As pages allocated by secretmem become unmovable, use CMA to back large page caches so that page allocator won't be surprised by failing attempt to migrate these pages. The CMA area used by secretmem is controlled by the "secretmem=" kernel parameter. This allows explicit control over the memory available for secretmem and provides upper hard limit for secretmem consumption. Link: https://lkml.kernel.org/r/20201203062949.5484-7-rppt@kernel.org Signed-off-by: Mike Rapoport <rppt@linux.ibm.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: David Hildenbrand <david@redhat.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 <palmer@dabbelt.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: Roman Gushchin <guro@fb.com> Cc: Shakeel Butt <shakeelb@google.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> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
-rw-r--r--mm/Kconfig2
-rw-r--r--mm/secretmem.c152
2 files changed, 135 insertions, 19 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index 6edd325b1f1d..7af1a55b708e 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -877,5 +877,7 @@ config KMAP_LOCAL
config SECRETMEM
def_bool ARCH_HAS_SET_DIRECT_MAP && !EMBEDDED
+ select GENERIC_ALLOCATOR
+ select CMA
endmenu
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 781aaaca8c70..52a900a135a5 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -7,12 +7,15 @@
#include <linux/mm.h>
#include <linux/fs.h>
+#include <linux/cma.h>
#include <linux/mount.h>
#include <linux/memfd.h>
#include <linux/bitops.h>
#include <linux/printk.h>
#include <linux/pagemap.h>
+#include <linux/genalloc.h>
#include <linux/syscalls.h>
+#include <linux/memblock.h>
#include <linux/pseudo_fs.h>
#include <linux/secretmem.h>
#include <linux/set_memory.h>
@@ -35,25 +38,80 @@
#define SECRETMEM_FLAGS_MASK SECRETMEM_MODE_MASK
struct secretmem_ctx {
+ struct gen_pool *pool;
unsigned int mode;
};
-static struct page *secretmem_alloc_page(gfp_t gfp)
+static struct cma *secretmem_cma;
+
+static int secretmem_pool_increase(struct secretmem_ctx *ctx, gfp_t gfp)
{
+ unsigned long nr_pages = (1 << PMD_PAGE_ORDER);
+ struct gen_pool *pool = ctx->pool;
+ unsigned long addr;
+ struct page *page;
+ int err;
+
+ page = cma_alloc(secretmem_cma, nr_pages, PMD_SIZE, gfp & __GFP_NOWARN);
+ if (!page)
+ return -ENOMEM;
+
+ err = set_direct_map_invalid_noflush(page, nr_pages);
+ if (err)
+ goto err_cma_release;
+
+ addr = (unsigned long)page_address(page);
+ err = gen_pool_add(pool, addr, PMD_SIZE, NUMA_NO_NODE);
+ if (err)
+ goto err_set_direct_map;
+
+ flush_tlb_kernel_range(addr, addr + PMD_SIZE);
+
+ return 0;
+
+err_set_direct_map:
/*
- * FIXME: use a cache of large pages to reduce the direct map
- * fragmentation
+ * If a split of PUD-size page was required, it already happened
+ * when we marked the pages invalid which guarantees that this call
+ * won't fail
*/
- return alloc_page(gfp);
+ set_direct_map_default_noflush(page, nr_pages);
+err_cma_release:
+ cma_release(secretmem_cma, page, nr_pages);
+ return err;
+}
+
+static struct page *secretmem_alloc_page(struct secretmem_ctx *ctx,
+ gfp_t gfp)
+{
+ struct gen_pool *pool = ctx->pool;
+ unsigned long addr;
+ struct page *page;
+ int err;
+
+ if (gen_pool_avail(pool) < PAGE_SIZE) {
+ err = secretmem_pool_increase(ctx, gfp);
+ if (err)
+ return NULL;
+ }
+
+ addr = gen_pool_alloc(pool, PAGE_SIZE);
+ if (!addr)
+ return NULL;
+
+ page = virt_to_page(addr);
+ get_page(page);
+
+ return page;
}
static vm_fault_t secretmem_fault(struct vm_fault *vmf)
{
+ struct secretmem_ctx *ctx = vmf->vma->vm_file->private_data;
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
struct inode *inode = file_inode(vmf->vma->vm_file);
pgoff_t offset = vmf->pgoff;
vm_fault_t ret = 0;
- unsigned long addr;
struct page *page;
int err;
@@ -62,8 +120,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
page = find_get_page(mapping, offset);
if (!page) {
-
- page = secretmem_alloc_page(vmf->gfp_mask);
+ page = secretmem_alloc_page(ctx, vmf->gfp_mask);
if (!page)
return vmf_error(-ENOMEM);
@@ -71,14 +128,8 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
if (unlikely(err))
goto err_put_page;
- err = set_direct_map_invalid_noflush(page, 1);
- if (err)
- goto err_del_page_cache;
-
- addr = (unsigned long)page_address(page);
- flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
-
__SetPageUptodate(page);
+ set_page_private(page, (unsigned long)ctx);
ret = VM_FAULT_LOCKED;
}
@@ -86,8 +137,6 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
vmf->page = page;
return ret;
-err_del_page_cache:
- delete_from_page_cache(page);
err_put_page:
put_page(page);
return vmf_error(err);
@@ -136,8 +185,11 @@ static int secretmem_migratepage(struct address_space *mapping,
static void secretmem_freepage(struct page *page)
{
- set_direct_map_default_noflush(page, 1);
- clear_highpage(page);
+ unsigned long addr = (unsigned long)page_address(page);
+ struct secretmem_ctx *ctx = (struct secretmem_ctx *)page_private(page);
+ struct gen_pool *pool = ctx->pool;
+
+ gen_pool_free(pool, addr, PAGE_SIZE);
}
static const struct address_space_operations secretmem_aops = {
@@ -172,13 +224,18 @@ static struct file *secretmem_file_create(unsigned long flags)
if (!ctx)
goto err_free_inode;
+ ctx->pool = gen_pool_create(PAGE_SHIFT, NUMA_NO_NODE);
+ if (!ctx->pool)
+ goto err_free_ctx;
+
file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
O_RDWR, &secretmem_fops);
if (IS_ERR(file))
- goto err_free_ctx;
+ goto err_free_pool;
mapping_set_unevictable(inode->i_mapping);
+ inode->i_private = ctx;
inode->i_mapping->private_data = ctx;
inode->i_mapping->a_ops = &secretmem_aops;
@@ -192,6 +249,8 @@ static struct file *secretmem_file_create(unsigned long flags)
return file;
+err_free_pool:
+ gen_pool_destroy(ctx->pool);
err_free_ctx:
kfree(ctx);
err_free_inode:
@@ -210,6 +269,9 @@ SYSCALL_DEFINE1(memfd_secret, unsigned long, flags)
if (flags & ~(SECRETMEM_FLAGS_MASK | O_CLOEXEC))
return -EINVAL;
+ if (!secretmem_cma)
+ return -ENOMEM;
+
fd = get_unused_fd_flags(flags & O_CLOEXEC);
if (fd < 0)
return fd;
@@ -230,11 +292,37 @@ err_put_fd:
return err;
}
+static void secretmem_cleanup_chunk(struct gen_pool *pool,
+ struct gen_pool_chunk *chunk, void *data)
+{
+ unsigned long start = chunk->start_addr;
+ unsigned long end = chunk->end_addr;
+ struct page *page = virt_to_page(start);
+ unsigned long nr_pages = (end - start + 1) / PAGE_SIZE;
+ int i;
+
+ set_direct_map_default_noflush(page, nr_pages);
+
+ for (i = 0; i < nr_pages; i++)
+ clear_highpage(page + i);
+
+ cma_release(secretmem_cma, page, nr_pages);
+}
+
+static void secretmem_cleanup_pool(struct secretmem_ctx *ctx)
+{
+ struct gen_pool *pool = ctx->pool;
+
+ gen_pool_for_each_chunk(pool, secretmem_cleanup_chunk, ctx);
+ gen_pool_destroy(pool);
+}
+
static void secretmem_evict_inode(struct inode *inode)
{
struct secretmem_ctx *ctx = inode->i_private;
truncate_inode_pages_final(&inode->i_data);
+ secretmem_cleanup_pool(ctx);
clear_inode(inode);
kfree(ctx);
}
@@ -271,3 +359,29 @@ static int secretmem_init(void)
return ret;
}
fs_initcall(secretmem_init);
+
+static int __init secretmem_setup(char *str)
+{
+ phys_addr_t align = PMD_SIZE;
+ unsigned long reserved_size;
+ int err;
+
+ reserved_size = memparse(str, NULL);
+ if (!reserved_size)
+ return 0;
+
+ if (reserved_size * 2 > PUD_SIZE)
+ align = PUD_SIZE;
+
+ err = cma_declare_contiguous(0, reserved_size, 0, align, 0, false,
+ "secretmem", &secretmem_cma);
+ if (err) {
+ pr_err("failed to create CMA: %d\n", err);
+ return err;
+ }
+
+ pr_info("reserved %luM\n", reserved_size >> 20);
+
+ return 0;
+}
+__setup("secretmem=", secretmem_setup);