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[PULL 19/33] util/mmap-alloc: Factor out reserving of a memory region to
From: |
Paolo Bonzini |
Subject: |
[PULL 19/33] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve() |
Date: |
Tue, 15 Jun 2021 15:38:41 +0200 |
From: David Hildenbrand <david@redhat.com>
We want to reserve a memory region without actually populating memory.
Let's factor that out.
Reviewed-by: Igor Kotrasinski <i.kotrasinsk@partner.samsung.com>
Acked-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com> for memory backend and machine
core
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210510114328.21835-3-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
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 24854064b4..223d66219c 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__)
@@ -104,7 +136,6 @@ void *qemu_ram_mmap(int fd,
int prot;
int flags;
int map_sync_flags = 0;
- int guardfd;
size_t offset;
size_t total;
void *guardptr;
@@ -116,30 +147,7 @@ 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;
}
--
2.31.1
- [PULL 11/33] esp: revert 75ef849696 "esp: correctly fill bus id with requested lun", (continued)
- [PULL 11/33] esp: revert 75ef849696 "esp: correctly fill bus id with requested lun", Paolo Bonzini, 2021/06/15
- [PULL 04/33] block/scsi: correctly emulate the VPD block limits page, Paolo Bonzini, 2021/06/15
- [PULL 15/33] softmmu/physmem: Mark shared anonymous memory RAM_SHARED, Paolo Bonzini, 2021/06/15
- [PULL 17/33] softmmu/physmem: Fix qemu_ram_remap() to handle shared anonymous memory, Paolo Bonzini, 2021/06/15
- [PULL 09/33] esp: handle non-DMA transfers from the target one byte at a time, Paolo Bonzini, 2021/06/15
- [PULL 23/33] softmmu/memory: Pass ram_flags to qemu_ram_alloc() and qemu_ram_alloc_internal(), Paolo Bonzini, 2021/06/15
- [PULL 22/33] softmmu/memory: Pass ram_flags to memory_region_init_ram_shared_nomigrate(), Paolo Bonzini, 2021/06/15
- [PULL 03/33] qemu-config: use qemu_opts_from_qdict, Paolo Bonzini, 2021/06/15
- [PULL 12/33] esp: correctly accumulate extended messages for PDMA, Paolo Bonzini, 2021/06/15
- [PULL 14/33] esp: store lun coming from the MESSAGE OUT phase, Paolo Bonzini, 2021/06/15
- [PULL 19/33] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(),
Paolo Bonzini <=
- [PULL 20/33] util/mmap-alloc: Factor out activating of memory to mmap_activate(), Paolo Bonzini, 2021/06/15
- [PULL 25/33] memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap(), Paolo Bonzini, 2021/06/15
- [PULL 33/33] configure: map x32 to cpu_family x86_64 for meson, Paolo Bonzini, 2021/06/15
- [PULL 30/33] hmp: Print "share" property of memory backends with "info memdev", Paolo Bonzini, 2021/06/15
- [PULL 18/33] util/mmap-alloc: Factor out calculation of the pagesize for the guard page, Paolo Bonzini, 2021/06/15
- [PULL 21/33] softmmu/memory: Pass ram_flags to qemu_ram_alloc_from_fd(), Paolo Bonzini, 2021/06/15
- [PULL 29/33] qmp: Include "share" property of memory backends, Paolo Bonzini, 2021/06/15
- [PULL 26/33] util/mmap-alloc: Support RAM_NORESERVE via MAP_NORESERVE under Linux, Paolo Bonzini, 2021/06/15
- [PULL 32/33] hmp: Print "reserve" property of memory backends with "info memdev", Paolo Bonzini, 2021/06/15
- [PULL 24/33] util/mmap-alloc: Pass flags instead of separate bools to qemu_ram_mmap(), Paolo Bonzini, 2021/06/15