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[RFC PATCH v2 1/3] exec/memory: Introduce memory_region_init_rom_device_
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From: |
Philippe Mathieu-Daudé |
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Subject: |
[RFC PATCH v2 1/3] exec/memory: Introduce memory_region_init_rom_device_from_file() |
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Date: |
Mon, 1 Mar 2021 12:53:27 +0100 |
Introduce memory_region_init_rom_device_from_file() which mmap
the backing file of ROM devices. This allows to reduce QEMU memory
footprint as the same file can be shared between multiple instances
of QEMU.
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
include/exec/memory.h | 85 +++++++++++++++++++++++++++++++++++++
softmmu/memory.c | 98 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 183 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index c6fb714e499..bacf7495003 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -487,6 +487,9 @@ struct MemoryRegion {
const char *name;
unsigned ioeventfd_nb;
MemoryRegionIoeventfd *ioeventfds;
+#ifndef CONFIG_POSIX
+ gchar *contents;
+#endif
};
struct IOMMUMemoryRegion {
@@ -1131,6 +1134,43 @@ void
memory_region_init_rom_device_nomigrate(MemoryRegion *mr,
uint64_t size,
Error **errp);
+/**
+ * memory_region_init_rom_device_from_file_nomigrate:
+ * Initialize a ROM memory region from the specified backing file.
+ * Writes are handled via callbacks.
+ *
+ * Note that this function does not do anything to cause the data in the
+ * RAM side of the memory region to be migrated; that is the responsibility
+ * of the caller.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @owner: the object that tracks the region's reference count
+ * @ops: callbacks for write access handling (must not be NULL).
+ * @opaque: passed to the read and write callbacks of the @ops structure.
+ * @name: Region name, becomes part of RAMBlock name used in migration stream
+ * must be unique within any device
+ * @size: size of the region.
+ * @ram_flags: specify the properties of the ram block, which can be one
+ * or bit-or of following values
+ * - RAM_SHARED: mmap the backing file or device with MAP_SHARED
+ * - RAM_PMEM: the backend @mem_path is persistent memory
+ * Other bits are ignored.
+ * @path: specify the backing file
+ * @readonly: true to open @path for reading, false for read/write.
+ * @errp: pointer to Error*, to store an error if it happens.
+ */
+void memory_region_init_rom_device_from_file_nomigrate(MemoryRegion *mr,
+ Object *owner,
+ const MemoryRegionOps
*ops,
+ void *opaque,
+ const char *name,
+ uint64_t size,
+ uint64_t align,
+ uint32_t ram_flags,
+ const char *path,
+ bool readonly,
+ Error **errp);
+
/**
* memory_region_init_iommu: Initialize a memory region of a custom type
* that translates addresses
@@ -1249,6 +1289,51 @@ void memory_region_init_rom_device(MemoryRegion *mr,
Error **errp);
+/**
+ * memory_region_init_rom_device_from_file:
+ * Initialize a ROM memory region from the specified backing file.
+ * Writes are handled via callbacks.
+ *
+ * This function initializes a memory region backed by RAM for reads
+ * and callbacks for writes, and arranges for the RAM backing to
+ * be migrated (by calling vmstate_register_ram()
+ * if @owner is a DeviceState, or vmstate_register_ram_global() if
+ * @owner is NULL).
+ *
+ * TODO: Currently we restrict @owner to being either NULL (for
+ * global RAM regions with no owner) or devices, so that we can
+ * give the RAM block a unique name for migration purposes.
+ * We should lift this restriction and allow arbitrary Objects.
+ * If you pass a non-NULL non-device @owner then we will assert.
+ *
+ * @mr: the #MemoryRegion to be initialized.
+ * @owner: the object that tracks the region's reference count
+ * @ops: callbacks for write access handling (must not be NULL).
+ * @opaque: passed to the read and write callbacks of the @ops structure.
+ * @name: Region name, becomes part of RAMBlock name used in migration stream
+ * must be unique within any device
+ * @size: size of the region.
+ * @ram_flags: specify the properties of the ram block, which can be one
+ * or bit-or of following values
+ * - RAM_SHARED: mmap the backing file or device with MAP_SHARED
+ * - RAM_PMEM: the backend @mem_path is persistent memory
+ * Other bits are ignored.
+ * @path: specify the backing file
+ * @readonly: true to open @path for reading, false for read/write.
+ * @errp: pointer to Error*, to store an error if it happens.
+ */
+void memory_region_init_rom_device_from_file(MemoryRegion *mr,
+ Object *owner,
+ const MemoryRegionOps *ops,
+ void *opaque,
+ const char *name,
+ uint64_t size,
+ uint64_t align,
+ uint32_t ram_flags,
+ const char *path,
+ bool readonly,
+ Error **errp);
+
/**
* memory_region_owner: get a memory region's owner.
*
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 874a8fccdee..ea1892a8cd6 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -1120,6 +1120,14 @@ static void memory_region_destructor_ram(MemoryRegion
*mr)
qemu_ram_free(mr->ram_block);
}
+#ifndef CONFIG_POSIX
+static void memory_region_destructor_contents(MemoryRegion *mr)
+{
+ qemu_ram_free(mr->ram_block);
+ g_free(mr->contents);
+}
+#endif
+
static bool memory_region_need_escape(char c)
{
return c == '/' || c == '[' || c == '\\' || c == ']';
@@ -1712,6 +1720,96 @@ void
memory_region_init_rom_device_nomigrate(MemoryRegion *mr,
}
}
+void memory_region_init_rom_device_from_file_nomigrate(MemoryRegion *mr,
+ Object *owner,
+ const MemoryRegionOps
*ops,
+ void *opaque,
+ const char *name,
+ uint64_t size,
+ uint64_t align,
+ uint32_t ram_flags,
+ const char *path,
+ bool readonly,
+ Error **errp)
+{
+ Error *err = NULL;
+
+ assert(ops);
+#ifdef CONFIG_POSIX
+ memory_region_init(mr, owner, name, size);
+ mr->opaque = opaque;
+ mr->ops = ops;
+ mr->rom_device = true;
+ mr->readonly = readonly;
+ mr->ram = true;
+ mr->align = align;
+ mr->terminates = true;
+ mr->destructor = memory_region_destructor_ram;
+ mr->ram_block = qemu_ram_alloc_from_file(size, mr, ram_flags, path,
+ readonly, &err);
+ if (err) {
+ mr->size = int128_zero();
+ object_unparent(OBJECT(mr));
+ error_propagate(errp, err);
+ }
+#else
+ g_autoptr(GError) gerr = NULL;
+ gsize len;
+
+ memory_region_init(mr, owner, name, size);
+ mr->ops = ops;
+ mr->opaque = opaque;
+ mr->terminates = true;
+ mr->rom_device = true;
+
+ if (!g_file_get_contents(path, &mr->contents, &len, &gerr)) {
+ error_setg(errp, "Unable to read '%s': %s", path, gerr->message);
+ return;
+ }
+ mr->destructor = memory_region_destructor_contents;
+ mr->contents = g_realloc(mr->contents, size);
+ mr->ram_block = qemu_ram_alloc_from_ptr(size, mr->contents, mr, &err);
+ if (err) {
+ mr->size = int128_zero();
+ object_unparent(OBJECT(mr));
+ error_propagate(errp, err);
+ }
+#endif
+}
+
+void memory_region_init_rom_device_from_file(MemoryRegion *mr,
+ Object *owner,
+ const MemoryRegionOps *ops,
+ void *opaque,
+ const char *name,
+ uint64_t size,
+ uint64_t align,
+ uint32_t ram_flags,
+ const char *path,
+ bool readonly,
+ Error **errp)
+{
+ DeviceState *owner_dev;
+ Error *err = NULL;
+
+ memory_region_init_rom_device_from_file_nomigrate(mr, owner, ops, opaque,
+ name, size, align,
+ ram_flags, path,
readonly,
+ &err);
+ if (err) {
+ error_propagate(errp, err);
+ return;
+ }
+ /* This will assert if owner is neither NULL nor a DeviceState.
+ * We only want the owner here for the purposes of defining a
+ * unique name for migration. TODO: Ideally we should implement
+ * a naming scheme for Objects which are not DeviceStates, in
+ * which case we can relax this restriction.
+ */
+ owner_dev = DEVICE(owner);
+ vmstate_register_ram(mr, owner_dev);
+}
+
void memory_region_init_iommu(void *_iommu_mr,
size_t instance_size,
const char *mrtypename,
--
2.26.2