If memory-backend-{file,ram} has a size that's not aligned to
underlying page size it is not only wasteful, but also may lead
to hard to debug behaviour. For instance, in case
memory-backend-file and hugepages, madvise() and mbind() fail.
Rightfully so, page is the smallest unit they can work with. And
even though an error is reported, the root cause it not very
clear:
qemu-system-x86_64: Couldn't set property 'dump' on 'memory-backend-file':
Invalid argument
After this commit:
qemu-system-x86_64: backend 'memory-backend-file' memory size must be
multiple of 2 MiB
Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
---
backends/hostmem.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 012a8c190f..4d6c69fe4d 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -20,6 +20,7 @@
#include "qom/object_interfaces.h"
#include "qemu/mmap-alloc.h"
#include "qemu/madvise.h"
+#include "qemu/cutils.h"
#include "hw/qdev-core.h"
#ifdef CONFIG_NUMA
@@ -337,6 +338,7 @@ host_memory_backend_memory_complete(UserCreatable *uc,
Error **errp)
HostMemoryBackendClass *bc = MEMORY_BACKEND_GET_CLASS(uc);
void *ptr;
uint64_t sz;
+ size_t pagesize;
bool async = !phase_check(PHASE_LATE_BACKENDS_CREATED);
if (!bc->alloc) {
@@ -348,6 +350,14 @@ host_memory_backend_memory_complete(UserCreatable *uc,
Error **errp)
ptr = memory_region_get_ram_ptr(&backend->mr);
sz = memory_region_size(&backend->mr);
+ pagesize = qemu_ram_pagesize(backend->mr.ram_block);
+
+ if (!QEMU_IS_ALIGNED(sz, pagesize)) {
+ g_autofree char *pagesize_str = size_to_str(pagesize);
+ error_setg(errp, "backend '%s' memory size must be multiple of %s",
+ object_get_typename(OBJECT(uc)), pagesize_str);
+ return;
+ }
if (backend->merge &&
qemu_madvise(ptr, sz, QEMU_MADV_MERGEABLE)) {
--
2.44.1
