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util/mmap-alloc: Factor out activating of memory to mmap_activate() 

We want to activate memory within a reserved memory region, to make it
accessible. Let's factor that out.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Acked-by: Murilo Opsfelder Araujo <muriloo@linux.ibm.com>
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: <20210510114328.21835-4-david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
master
David Hildenbrand 2021-05-10 13:43:16 +02:00 committed by Paolo Bonzini
parent 01c26ad6af
commit d01cbf82ce
1 changed files with 50 additions and 44 deletions
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94
util/mmap-alloc.c
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@ -114,6 +114,52 @@ static void *mmap_reserve(size_t size, int fd)
return mmap(0, size, PROT_NONE, flags, fd, 0);
}
/*
* Activate memory in a reserved region from the given fd (if any), to make
* it accessible.
*/
static void *mmap_activate(void *ptr, size_t size, int fd, bool readonly,
bool shared, bool is_pmem, off_t map_offset)
{
const int prot = PROT_READ | (readonly ? 0 : PROT_WRITE);
int map_sync_flags = 0;
int flags = MAP_FIXED;
void *activated_ptr;
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
flags |= shared ? MAP_SHARED : MAP_PRIVATE;
if (shared && is_pmem) {
map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE;
}
activated_ptr = mmap(ptr, size, prot, flags | map_sync_flags, fd,
map_offset);
if (activated_ptr == MAP_FAILED && map_sync_flags) {
if (errno == ENOTSUP) {
char *proc_link = g_strdup_printf("/proc/self/fd/%d", fd);
char *file_name = g_malloc0(PATH_MAX);
int len = readlink(proc_link, file_name, PATH_MAX - 1);
if (len < 0) {
len = 0;
}
file_name[len] = '\0';
fprintf(stderr, "Warning: requesting persistence across crashes "
"for backend file %s failed. Proceeding without "
"persistence, data might become corrupted in case of host "
"crash.\n", file_name);
g_free(proc_link);
g_free(file_name);
}
/*
* If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, we will try
* again without these flags to handle backwards compatibility.
*/
activated_ptr = mmap(ptr, size, prot, flags, fd, map_offset);
}
return activated_ptr;
}
static inline size_t mmap_guard_pagesize(int fd)
{
#if defined(__powerpc64__) && defined(__linux__)
@ -133,13 +179,8 @@ void *qemu_ram_mmap(int fd,
off_t map_offset)
{
const size_t guard_pagesize = mmap_guard_pagesize(fd);
int prot;
int flags;
int map_sync_flags = 0;
size_t offset;
size_t total;
void *guardptr;
void *ptr;
size_t offset, total;
void *ptr, *guardptr;
/*
* Note: this always allocates at least one extra page of virtual address
@ -156,45 +197,10 @@ void *qemu_ram_mmap(int fd,
/* Always align to host page size */
assert(align >= guard_pagesize);
flags = MAP_FIXED;
flags |= fd == -1 ? MAP_ANONYMOUS : 0;
flags |= shared ? MAP_SHARED : MAP_PRIVATE;
if (shared && is_pmem) {
map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE;
}
offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr;
prot = PROT_READ | (readonly ? 0 : PROT_WRITE);
ptr = mmap(guardptr + offset, size, prot,
flags | map_sync_flags, fd, map_offset);
if (ptr == MAP_FAILED && map_sync_flags) {
if (errno == ENOTSUP) {
char *proc_link, *file_name;
int len;
proc_link = g_strdup_printf("/proc/self/fd/%d", fd);
file_name = g_malloc0(PATH_MAX);
len = readlink(proc_link, file_name, PATH_MAX - 1);
if (len < 0) {
len = 0;
}
file_name[len] = '\0';
fprintf(stderr, "Warning: requesting persistence across crashes "
"for backend file %s failed. Proceeding without "
"persistence, data might become corrupted in case of host "
"crash.\n", file_name);
g_free(proc_link);
g_free(file_name);
}
/*
* if map failed with MAP_SHARED_VALIDATE | MAP_SYNC,
* we will remove these flags to handle compatibility.
*/
ptr = mmap(guardptr + offset, size, prot, flags, fd, map_offset);
}
ptr = mmap_activate(guardptr + offset, size, fd, readonly, shared, is_pmem,
map_offset);
if (ptr == MAP_FAILED) {
munmap(guardptr, total);
return MAP_FAILED;