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[PATCH v3 08/15] util/mmap-alloc: Factor out reserving of a memory regio
From: |
David Hildenbrand |
Subject: |
[PATCH v3 08/15] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve() |
Date: |
Thu, 27 Feb 2020 11:11:58 +0100 |
We want to reserve a memory region without actually populating memory.
Let's factor that out.
Reviewed-by: Igor Kotrasinski <address@hidden>
Acked-by: Murilo Opsfelder Araujo <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Reviewed-by: Peter Xu <address@hidden>
Cc: "Michael S. Tsirkin" <address@hidden>
Cc: Greg Kurz <address@hidden>
Cc: Murilo Opsfelder Araujo <address@hidden>
Cc: Eduardo Habkost <address@hidden>
Cc: "Dr. David Alan Gilbert" <address@hidden>
Cc: Igor Mammedov <address@hidden>
Signed-off-by: David Hildenbrand <address@hidden>
---
util/mmap-alloc.c | 58 +++++++++++++++++++++++++++--------------------
1 file changed, 33 insertions(+), 25 deletions(-)
diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
index f0277f9fad..9e9534a07e 100644
--- a/util/mmap-alloc.c
+++ b/util/mmap-alloc.c
@@ -82,6 +82,38 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
return qemu_real_host_page_size;
}
+/*
+ * Reserve a new memory region of the requested size to be used for mapping
+ * from the given fd (if any).
+ */
+static void *mmap_reserve(size_t size, int fd)
+{
+ int flags = MAP_PRIVATE;
+
+#if defined(__powerpc64__) && defined(__linux__)
+ /*
+ * On ppc64 mappings in the same segment (aka slice) must share the same
+ * page size. Since we will be re-allocating part of this segment
+ * from the supplied fd, we should make sure to use the same page size, to
+ * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
+ * avoid allocating backing store memory.
+ * We do this unless we are using the system page size, in which case
+ * anonymous memory is OK.
+ */
+ if (fd == -1 || qemu_fd_getpagesize(fd) == qemu_real_host_page_size) {
+ fd = -1;
+ flags |= MAP_ANONYMOUS;
+ } else {
+ flags |= MAP_NORESERVE;
+ }
+#else
+ fd = -1;
+ flags |= MAP_ANONYMOUS;
+#endif
+
+ return mmap(0, size, PROT_NONE, flags, fd, 0);
+}
+
static inline size_t mmap_guard_pagesize(int fd)
{
#if defined(__powerpc64__) && defined(__linux__)
@@ -101,7 +133,6 @@ void *qemu_ram_mmap(int fd,
const size_t guard_pagesize = mmap_guard_pagesize(fd);
int flags;
int map_sync_flags = 0;
- int guardfd;
size_t offset;
size_t total;
void *guardptr;
@@ -113,30 +144,7 @@ void *qemu_ram_mmap(int fd,
*/
total = size + align;
-#if defined(__powerpc64__) && defined(__linux__)
- /* On ppc64 mappings in the same segment (aka slice) must share the same
- * page size. Since we will be re-allocating part of this segment
- * from the supplied fd, we should make sure to use the same page size, to
- * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
- * avoid allocating backing store memory.
- * We do this unless we are using the system page size, in which case
- * anonymous memory is OK.
- */
- flags = MAP_PRIVATE;
- if (fd == -1 || guard_pagesize == qemu_real_host_page_size) {
- guardfd = -1;
- flags |= MAP_ANONYMOUS;
- } else {
- guardfd = fd;
- flags |= MAP_NORESERVE;
- }
-#else
- guardfd = -1;
- flags = MAP_PRIVATE | MAP_ANONYMOUS;
-#endif
-
- guardptr = mmap(0, total, PROT_NONE, flags, guardfd, 0);
-
+ guardptr = mmap_reserve(total, fd);
if (guardptr == MAP_FAILED) {
return MAP_FAILED;
}
--
2.24.1
- [PATCH v3 00/15] Ram blocks with resizeable anonymous allocations under POSIX, David Hildenbrand, 2020/02/27
- [PATCH v3 01/15] util: vfio-helpers: Fix qemu_vfio_close(), David Hildenbrand, 2020/02/27
- [PATCH v3 02/15] util: vfio-helpers: Remove Error parameter from qemu_vfio_undo_mapping(), David Hildenbrand, 2020/02/27
- [PATCH v3 03/15] util: vfio-helpers: Factor out removal from qemu_vfio_undo_mapping(), David Hildenbrand, 2020/02/27
- [PATCH v3 04/15] exec: Factor out setting ram settings (madvise ...) into qemu_ram_apply_settings(), David Hildenbrand, 2020/02/27
- [PATCH v3 05/15] exec: Reuse qemu_ram_apply_settings() in qemu_ram_remap(), David Hildenbrand, 2020/02/27
- [PATCH v3 06/15] exec: Drop "shared" parameter from ram_block_add(), David Hildenbrand, 2020/02/27
- [PATCH v3 07/15] util/mmap-alloc: Factor out calculation of the pagesize for the guard page, David Hildenbrand, 2020/02/27
- [PATCH v3 08/15] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(),
David Hildenbrand <=
- [PATCH v3 09/15] util/mmap-alloc: Factor out populating of memory to mmap_populate(), David Hildenbrand, 2020/02/27
- [PATCH v3 10/15] util/mmap-alloc: Prepare for resizeable mmaps, David Hildenbrand, 2020/02/27
- [PATCH v3 11/15] util/mmap-alloc: Implement resizeable mmaps, David Hildenbrand, 2020/02/27
- [PATCH v3 12/15] util: vfio-helpers: Implement ram_block_resized(), David Hildenbrand, 2020/02/27
- Re: [PATCH v3 12/15] util: vfio-helpers: Implement ram_block_resized(), Peter Xu, 2020/02/28