[PATCH] backends/hostmem: Fix support of memory-backend-memfd in qemu_maxrampagesize()

[Thomas Huth <thuth@redhat.com>]

It is currently not possible yet to use "memory-backend-memfd" on s390x
with hugepages enabled. This problem is caused by qemu_maxrampagesize()
not taking memory-backend-memfd objects into account yet, so the code
in s390_memory_init() fails to enable the huge page support there via
s390_set_max_pagesize(). Fix it by looking at the memory-backend-memfd
in the host_memory_backend_pagesize() function, too.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2116496
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 include/sysemu/hostmem.h |  8 +++++++-
 backends/hostmem-memfd.c |  2 --
 backends/hostmem.c       | 27 +++++++++++++++++----------
 3 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 9ff5c16963..d983ae6c01 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -34,10 +34,16 @@ OBJECT_DECLARE_TYPE(HostMemoryBackend, HostMemoryBackendClass,
 /* hostmem-file.c */
 /**
  * @TYPE_MEMORY_BACKEND_FILE:
- * name of backend that uses mmap on a file descriptor
+ * name of backend that uses mmap on a file
  */
 #define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
 
+/* hostmem-memfd.c */
+/**
+ * @TYPE_MEMORY_BACKEND_MEMFD:
+ * name of backend that uses mmap on a memfd file descriptor
+ */
+#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
 
 /**
  * HostMemoryBackendClass:
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 3fc85c3db8..1ab2085e49 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -18,8 +18,6 @@
 #include "qapi/error.h"
 #include "qom/object.h"
 
-#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
-
 OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendMemfd, MEMORY_BACKEND_MEMFD)
 
 
diff --git a/backends/hostmem.c b/backends/hostmem.c
index 624bb7ecd3..ebce887105 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -306,22 +306,29 @@ bool host_memory_backend_is_mapped(HostMemoryBackend *backend)
     return backend->is_mapped;
 }
 
-#ifdef __linux__
 size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
 {
+    size_t pagesize = 0;
+
+#ifdef __linux__
     Object *obj = OBJECT(memdev);
-    char *path = object_property_get_str(obj, "mem-path", NULL);
-    size_t pagesize = qemu_mempath_getpagesize(path);
 
-    g_free(path);
+    if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND_FILE)) {
+        char *path = object_property_get_str(obj, "mem-path", NULL);
+        pagesize = qemu_mempath_getpagesize(path);
+        g_free(path);
+    } else if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND_MEMFD) &&
+               object_property_get_bool(obj, "hugetlb", &error_abort)) {
+        pagesize = object_property_get_int(obj, "hugetlbsize", &error_abort);
+    }
+#endif
+
+    if (!pagesize) {
+        pagesize = qemu_real_host_page_size();
+    }
+
     return pagesize;
 }
-#else
-size_t host_memory_backend_pagesize(HostMemoryBackend *memdev)
-{
-    return qemu_real_host_page_size();
-}
-#endif
 
 static void
 host_memory_backend_memory_complete(UserCreatable *uc, Error **errp)
-- 
2.31.1