Add a variant of mmap_anon_or_hugetlbfs() that allocates memory
aligned as specified. This function doesn't map or allocate more
memory than the requested amount.
Signed-off-by: Fuad Tabba <tabba@xxxxxxxxxx>
---
util/util.c | 41 ++++++++++++++++++++++++++++++++++++++---
1 file changed, 38 insertions(+), 3 deletions(-)
diff --git a/util/util.c b/util/util.c
index 54c2b26..9f83d70 100644
--- a/util/util.c
+++ b/util/util.c
@@ -120,10 +120,17 @@ int memfd_alloc(u64 size, bool hugetlb, u64 blk_size)
return fd;
}
-/* This function wraps the decision between hugetlbfs map (if requested) or normal mmap */
-void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *hugetlbfs_path, u64 size)
+/*
+ * This function allocates memory aligned to align_sz.
+ * It also wraps the decision between hugetlbfs (if requested) or normal mmap.
+ */
+void *mmap_anon_or_hugetlbfs_align(struct kvm *kvm, const char *hugetlbfs_path,
+ u64 size, u64 align_sz)
{
u64 blk_size = 0;
+ u64 total_map = size + align_sz;
+ u64 start_off, end_off;
+ void *addr_map, *addr_align;
int fd;
/*
@@ -143,10 +150,38 @@ void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *hugetlbfs_path, u64 si
kvm->ram_pagesize = getpagesize();
}
+ /* Create a mapping with room for alignment without allocating. */
+ addr_map = mmap(NULL, total_map, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ if (addr_map == MAP_FAILED)
+ return MAP_FAILED;
+
fd = memfd_alloc(size, hugetlbfs_path, blk_size);
if (fd < 0)
return MAP_FAILED;
+ /* Map the allocated memory in the fd to the specified alignment. */
+ addr_align = (void *)ALIGN((u64)addr_map, align_sz);
+ if (mmap(addr_align, size, PROT_RW, MAP_PRIVATE | MAP_FIXED, fd, 0) ==
+ MAP_FAILED) {
+ close(fd);
+ return MAP_FAILED;
+ }
+
+ /* Remove the mapping for unused address ranges. */
+ start_off = addr_align - addr_map;
+ if (start_off)
+ munmap(addr_map, start_off);
+
+ end_off = align_sz - start_off;
+ if (end_off)
+ munmap((void *)((u64)addr_align + size), end_off);
+
kvm->ram_fd = fd;
- return mmap(NULL, size, PROT_RW, MAP_PRIVATE, kvm->ram_fd, 0);
+ return addr_align;
+}
+
+void *mmap_anon_or_hugetlbfs(struct kvm *kvm, const char *hugetlbfs_path, u64 size)
+{
+ return mmap_anon_or_hugetlbfs_align(kvm, hugetlbfs_path, size, 0);
}
--
2.39.0.rc0.267.gcb52ba06e7-goog
