diff mbox series

[V4,03/19] memory: add RAM_PRIVATE

Message ID 1733145611-62315-4-git-send-email-steven.sistare@oracle.com (mailing list archive)
State New
Headers show
Series Live update: cpr-transfer | expand

Commit Message

Steven Sistare Dec. 2, 2024, 1:19 p.m. UTC 
Define the RAM_PRIVATE flag.

In RAMBlock creation functions, if MAP_SHARED is 0 in the flags parameter,
in a subsequent patch the implementation may still create a shared mapping
if other conditions require it.  Callers who specifically want a private
mapping, eg for objects specified by the user, must pass RAM_PRIVATE.

After RAMBlock creation, MAP_SHARED in the block's flags indicates whether
the block is shared or private, and MAP_PRIVATE is omitted.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 backends/hostmem-epc.c   |  2 +-
 backends/hostmem-file.c  |  2 +-
 backends/hostmem-memfd.c |  2 +-
 backends/hostmem-ram.c   |  2 +-
 include/exec/memory.h    | 10 ++++++++++
 system/physmem.c         | 15 ++++++++++++---
 6 files changed, 26 insertions(+), 7 deletions(-)

Comments

Peter Xu Dec. 9, 2024, 7:45 p.m. UTC | #1 
On Mon, Dec 02, 2024 at 05:19:55AM -0800, Steve Sistare wrote:
> Define the RAM_PRIVATE flag.
> 
> In RAMBlock creation functions, if MAP_SHARED is 0 in the flags parameter,
> in a subsequent patch the implementation may still create a shared mapping
> if other conditions require it.  Callers who specifically want a private
> mapping, eg for objects specified by the user, must pass RAM_PRIVATE.
> 
> After RAMBlock creation, MAP_SHARED in the block's flags indicates whether
> the block is shared or private, and MAP_PRIVATE is omitted.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

diff --git a/backends/hostmem-epc.c b/backends/hostmem-epc.c
index 6c024d6..3148ffa 100644
--- a/backends/hostmem-epc.c
+++ b/backends/hostmem-epc.c
@@ -36,7 +36,7 @@  sgx_epc_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 
     backend->aligned = true;
     name = object_get_canonical_path(OBJECT(backend));
-    ram_flags = (backend->share ? RAM_SHARED : 0) | RAM_PROTECTED;
+    ram_flags = (backend->share ? RAM_SHARED : RAM_PRIVATE) | RAM_PROTECTED;
     return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
                                           backend->size, ram_flags, fd, 0, errp);
 }
diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
index 7e5072e..8cc10cb 100644
--- a/backends/hostmem-file.c
+++ b/backends/hostmem-file.c
@@ -82,7 +82,7 @@  file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 
     backend->aligned = true;
     name = host_memory_backend_get_name(backend);
-    ram_flags = backend->share ? RAM_SHARED : 0;
+    ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     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;
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
index 9f890a8..1bcae4b 100644
--- a/backends/hostmem-memfd.c
+++ b/backends/hostmem-memfd.c
@@ -52,7 +52,7 @@  memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
 
     backend->aligned = true;
     name = host_memory_backend_get_name(backend);
-    ram_flags = backend->share ? RAM_SHARED : 0;
+    ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
     ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
     return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name,
diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
index f7d81af..b380563 100644
--- a/backends/hostmem-ram.c
+++ b/backends/hostmem-ram.c
@@ -28,7 +28,7 @@  ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
     }
 
     name = host_memory_backend_get_name(backend);
-    ram_flags = backend->share ? RAM_SHARED : 0;
+    ram_flags = backend->share ? RAM_SHARED : RAM_PRIVATE;
     ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
     ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
     return memory_region_init_ram_flags_nomigrate(&backend->mr, OBJECT(backend),
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 9458e28..0ac21cc 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -246,6 +246,16 @@  typedef struct IOMMUTLBEvent {
 /* RAM can be private that has kvm guest memfd backend */
 #define RAM_GUEST_MEMFD   (1 << 12)
 
+/*
+ * In RAMBlock creation functions, if MAP_SHARED is 0 in the flags parameter,
+ * the implementation may still create a shared mapping if other conditions
+ * require it.  Callers who specifically want a private mapping, eg objects
+ * specified by the user, must pass RAM_PRIVATE.
+ * After RAMBlock creation, MAP_SHARED in the block's flags indicates whether
+ * the block is shared or private, and MAP_PRIVATE is omitted.
+ */
+#define RAM_PRIVATE (1 << 13)
+
 static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
                                        IOMMUNotifierFlag flags,
                                        hwaddr start, hwaddr end,
diff --git a/system/physmem.c b/system/physmem.c
index b0c4b22..36f0811 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -1949,7 +1949,11 @@  RAMBlock *qemu_ram_alloc_from_fd(ram_addr_t size, MemoryRegion *mr,
 {
     RAMBlock *new_block;
     Error *local_err = NULL;
-    int64_t file_size, file_align;
+    int64_t file_size, file_align, share_flags;
+
+    share_flags = ram_flags & (RAM_PRIVATE | RAM_SHARED);
+    assert(share_flags != (RAM_SHARED | RAM_PRIVATE));
+    ram_flags &= ~RAM_PRIVATE;
 
     /* Just support these ram flags by now. */
     assert((ram_flags & ~(RAM_SHARED | RAM_PMEM | RAM_NORESERVE |
@@ -2132,7 +2136,11 @@  RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
 {
     RAMBlock *new_block;
     Error *local_err = NULL;
-    int align;
+    int align, share_flags;
+
+    share_flags = ram_flags & (RAM_PRIVATE | RAM_SHARED);
+    assert(share_flags != (RAM_SHARED | RAM_PRIVATE));
+    ram_flags &= ~RAM_PRIVATE;
 
     assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
                           RAM_NORESERVE | RAM_GUEST_MEMFD)) == 0);
@@ -2183,7 +2191,8 @@  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)) == 0);
+    assert((ram_flags & ~(RAM_SHARED | RAM_NORESERVE | RAM_GUEST_MEMFD |
+                          RAM_PRIVATE)) == 0);
     return qemu_ram_alloc_internal(size, size, NULL, NULL, ram_flags, mr, errp);
 }