backends/hostmem: Report error when memory size is unaligned
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 <mprivozn@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Message-ID: <b5b9f9c6bba07879fb43f3c6f496c69867ae3716.1717584048.git.mprivozn@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/backends/hostmem-epc.c b/backends/hostmem-epc.c
index 735e2e1..f58fcf0 100644
--- a/backends/hostmem-epc.c
+++ b/backends/hostmem-epc.c
@@ -36,6 +36,7 @@
return false;
}
+ backend->aligned = true;
name = object_get_canonical_path(OBJECT(backend));
ram_flags = (backend->share ? RAM_SHARED : 0) | RAM_PROTECTED;
return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 3c69db7..7e5072e 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -80,6 +80,7 @@
g_assert_not_reached();
}
+ backend->aligned = true;
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
ram_flags |= fb->readonly ? RAM_READONLY_FD : 0;
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 745ead0..6a3c89a 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -52,6 +52,7 @@
return false;
}
+ backend->aligned = true;
name = host_memory_backend_get_name(backend);
ram_flags = backend->share ? RAM_SHARED : 0;
ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
diff --git a/backends/hostmem.c b/backends/hostmem.c
index eb9682b..1edc0ed 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
@@ -325,6 +326,7 @@
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) {
@@ -336,6 +338,14 @@
ptr = memory_region_get_ram_ptr(&backend->mr);
sz = memory_region_size(&backend->mr);
+ pagesize = qemu_ram_pagesize(backend->mr.ram_block);
+
+ if (backend->aligned && !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);
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 04b884b..de47ae5 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -74,7 +74,7 @@
uint64_t size;
bool merge, dump, use_canonical_path;
bool prealloc, is_mapped, share, reserve;
- bool guest_memfd;
+ bool guest_memfd, aligned;
uint32_t prealloc_threads;
ThreadContext *prealloc_context;
DECLARE_BITMAP(host_nodes, MAX_NODES + 1);
