This name is too generic, and can conflict with in-place guest-memfd
support.  Add a _PRIVATE suffix to show what it really means: it is always
silently using an internal guest-memfd to back a shared host backend,
rather than used in-place.

This paves way for in-place guest-memfd, which means we can have a ramblock
that allocates pages completely from guest-memfd (private or shared).

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/system/memory.h   | 8 ++++----
 include/system/ram_addr.h | 2 +-
 backends/hostmem-file.c   | 2 +-
 backends/hostmem-memfd.c  | 2 +-
 backends/hostmem-ram.c    | 2 +-
 system/memory.c           | 2 +-
 system/physmem.c          | 8 ++++----
 7 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/system/memory.h b/include/system/memory.h
index 3bd5ffa5e0..2c1a5e06b4 100644
--- a/include/system/memory.h
+++ b/include/system/memory.h
@@ -263,7 +263,7 @@ typedef struct IOMMUTLBEvent {
 #define RAM_READONLY_FD (1 << 11)
 
 /* RAM can be private that has kvm guest memfd backend */
-#define RAM_GUEST_MEMFD   (1 << 12)
+#define RAM_GUEST_MEMFD_PRIVATE   (1 << 12)
 
 /*
  * In RAMBlock creation functions, if MAP_SHARED is 0 in the flags parameter,
@@ -1401,7 +1401,7 @@ bool memory_region_init_ram_nomigrate(MemoryRegion *mr,
  *        must be unique within any device
  * @size: size of the region.
  * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_NORESERVE,
- *             RAM_GUEST_MEMFD.
+ *             RAM_GUEST_MEMFD_PRIVATE.
  * @errp: pointer to Error*, to store an error if it happens.
  *
  * Note that this function does not do anything to cause the data in the
@@ -1463,7 +1463,7 @@ bool memory_region_init_resizeable_ram(MemoryRegion *mr,
  *         (getpagesize()) will be used.
  * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
  *             RAM_NORESERVE, RAM_PROTECTED, RAM_NAMED_FILE, RAM_READONLY,
- *             RAM_READONLY_FD, RAM_GUEST_MEMFD
+ *             RAM_READONLY_FD, RAM_GUEST_MEMFD_PRIVATE
  * @path: the path in which to allocate the RAM.
  * @offset: offset within the file referenced by path
  * @errp: pointer to Error*, to store an error if it happens.
@@ -1493,7 +1493,7 @@ bool memory_region_init_ram_from_file(MemoryRegion *mr,
  * @size: size of the region.
  * @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
  *             RAM_NORESERVE, RAM_PROTECTED, RAM_NAMED_FILE, RAM_READONLY,
- *             RAM_READONLY_FD, RAM_GUEST_MEMFD
+ *             RAM_READONLY_FD, RAM_GUEST_MEMFD_PRIVATE
  * @fd: the fd to mmap.
  * @offset: offset within the file referenced by fd
  * @errp: pointer to Error*, to store an error if it happens.
diff --git a/include/system/ram_addr.h b/include/system/ram_addr.h
index 683485980c..930d3824d7 100644
--- a/include/system/ram_addr.h
+++ b/include/system/ram_addr.h
@@ -92,7 +92,7 @@ static inline unsigned long int ramblock_recv_bitmap_offset(void *host_addr,
  *  @resized: callback after calls to qemu_ram_resize
  *  @ram_flags: RamBlock flags. Supported flags: RAM_SHARED, RAM_PMEM,
  *              RAM_NORESERVE, RAM_PROTECTED, RAM_NAMED_FILE, RAM_READONLY,
- *              RAM_READONLY_FD, RAM_GUEST_MEMFD
+ *              RAM_READONLY_FD, RAM_GUEST_MEMFD_PRIVATE
  *  @mem_path or @fd: specify the backing file or device
  *  @offset: Offset into target file
  *  @grow: extend file if necessary (but an empty file is always extended).
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 8e3219c061..1f20cd8fd6 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -86,7 +86,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
     ram_flags |= fb->readonly ? RAM_READONLY_FD : 0;
     ram_flags |= fb->rom == ON_OFF_AUTO_ON ? RAM_READONLY : 0;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
-    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
+    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD_PRIVATE : 0;
     ram_flags |= fb->is_pmem ? RAM_PMEM : 0;
     ram_flags |= RAM_NAMED_FILE;
     return memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name,
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 923239f9cf..3f3e485709 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -60,7 +60,7 @@ have_fd:
     backend->aligned = true;
     ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
-    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
+    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD_PRIVATE : 0;
     return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
                                           backend->size, ram_flags, fd, 0, errp);
 }
diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
index 062b1abb11..96ad29112d 100644
--- a/backends/hostmem-ram.c
+++ b/backends/hostmem-ram.c
@@ -30,7 +30,7 @@ ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
     name = host_memory_backend_get_name(backend);
     ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
-    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
+    ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD_PRIVATE : 0;
     return memory_region_init_ram_flags_nomigrate(&backend->mr, OBJECT(backend),
                                                   name, backend->size,
                                                   ram_flags, errp);
diff --git a/system/memory.c b/system/memory.c
index 8b84661ae3..006b03ce1c 100644
--- a/system/memory.c
+++ b/system/memory.c
@@ -3755,7 +3755,7 @@ bool memory_region_init_ram_guest_memfd(MemoryRegion *mr,
     DeviceState *owner_dev;
 
     if (!memory_region_init_ram_flags_nomigrate(mr, owner, name, size,
-                                                RAM_GUEST_MEMFD, errp)) {
+                                                RAM_GUEST_MEMFD_PRIVATE, errp)) {
         return false;
     }
     /* This will assert if owner is neither NULL nor a DeviceState.
diff --git a/system/physmem.c b/system/physmem.c
index a340ca3e61..1a186739a8 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2203,7 +2203,7 @@ static void ram_block_add(RAMBlock *new_block, Error **errp)
         }
     }
 
-    if (new_block->flags & RAM_GUEST_MEMFD) {
+    if (new_block->flags & RAM_GUEST_MEMFD_PRIVATE) {
         int ret;
 
         if (!kvm_enabled()) {
@@ -2333,7 +2333,7 @@ RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, ram_addr_t max_size,
     /* Just support these ram flags by now. */
     assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE |
                           RAM_PROTECTED | RAM_NAMED_FILE | RAM_READONLY |
-                          RAM_READONLY_FD | RAM_GUEST_MEMFD |
+                          RAM_READONLY_FD | RAM_GUEST_MEMFD_PRIVATE |
                           RAM_RESIZEABLE)) == 0);
     assert(max_size >= size);
 
@@ -2490,7 +2490,7 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
     ram_flags &= ~RAM_PRIVATE;
 
     assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
-                          RAM_NORESERVE | RAM_GUEST_MEMFD)) == 0);
+                          RAM_NORESERVE | RAM_GUEST_MEMFD_PRIVATE)) == 0);
     assert(!host ^ (ram_flags & RAM_PREALLOC));
     assert(max_size >= size);
 
@@ -2573,7 +2573,7 @@ RAMBlock *qemu_ram_alloc_from_ptr(ram_addr_t size, void *host,
 RAMBlock *qemu_ram_alloc(ram_addr_t size, uint32_t ram_flags,
                          MemoryRegion *mr, Error **errp)
 {
-    assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE | RAM_GUEST_MEMFD |
+    assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE | RAM_GUEST_MEMFD_PRIVATE |
                           RAM_PRIVATE)) == 0);
     return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp);
 }
-- 
2.50.1

On 10/24/2025 2:59 AM, Peter Xu wrote:
> This name is too generic, and can conflict with in-place guest-memfd
> support.  Add a _PRIVATE suffix to show what it really means: it is always
> silently using an internal guest-memfd to back a shared host backend,
> rather than used in-place.
> 
> This paves way for in-place guest-memfd, which means we can have a ramblock
> that allocates pages completely from guest-memfd (private or shared).

It's for patch 4-7. Regarding the rename. How about:

- RAM_GUEST_MEMFD => RAM_PRIVATE_MEMORY
- backend->guest_memfd => backend->private_memory
- machine_require_guest_memfd() => machine_require_private_memory()
- cgs->require_guest_memfd => cgs->require_private_memory

For CoCo VMs, what they require is the support of private memory, while 
the guest_memfd is how linux provides private memory support. But with 
mmap support added to guest memfd, it can serve as shared/non-private 
memory as well. Futher, in the future when in-place conversion support 
is implemented, a single guest memfd can serve as both shared and 
private in different parts. So guest_memfd_private will be confusing at 
that time.