Re: [Qemu-devel] [PATCH v3 05/34] add memdev backend infrastructure

[Peter Crosthwaite]

On Tue, May 27, 2014 at 11:01 PM, Igor Mammedov <address@hidden> wrote:
> Provides framework for splitting host RAM allocation/
> policies into a separate backend that could be used
> by devices.
>
> Initially only legacy RAM backend is provided, which
> uses memory_region_init_ram() allocator and compatible
> with every CLI option that affects memory_region_init_ram().
>
> Signed-off-by: Igor Mammedov <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> v4:
>  - don't use nonexisting anymore error_is_set()
> v3:
>  - fix path leak & use object_get_canonical_path_component()
>    for getting object name
> v2:
>  - reuse UserCreatable interface instead of custom callbacks
> ---
>  backends/Makefile.objs   |    2 +
>  backends/hostmem-ram.c   |   54 ++++++++++++++++++++++
>  backends/hostmem.c       |  113 
> ++++++++++++++++++++++++++++++++++++++++++++++
>  include/sysemu/hostmem.h |   60 ++++++++++++++++++++++++
>  4 files changed, 229 insertions(+), 0 deletions(-)
>  create mode 100644 backends/hostmem-ram.c
>  create mode 100644 backends/hostmem.c
>  create mode 100644 include/sysemu/hostmem.h
>
> diff --git a/backends/Makefile.objs b/backends/Makefile.objs
> index 591ddcf..7fb7acd 100644
> --- a/backends/Makefile.objs
> +++ b/backends/Makefile.objs
> @@ -6,3 +6,5 @@ common-obj-$(CONFIG_BRLAPI) += baum.o
>  baum.o-cflags := $(SDL_CFLAGS)
>
>  common-obj-$(CONFIG_TPM) += tpm.o
> +
> +common-obj-y += hostmem.o hostmem-ram.o
> diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c
> new file mode 100644
> index 0000000..cbf7e5a
> --- /dev/null
> +++ b/backends/hostmem-ram.c
> @@ -0,0 +1,54 @@
> +/*
> + * QEMU Host Memory Backend
> + *
> + * Copyright (C) 2013 Red Hat Inc
> + *
> + * Authors:
> + *   Igor Mammedov <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#include "sysemu/hostmem.h"
> +#include "qom/object_interfaces.h"
> +
> +#define TYPE_MEMORY_BACKEND_RAM "memory-ram"
> +
> +
> +static void
> +ram_backend_memory_init(UserCreatable *uc, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(uc);
> +    char *path;
> +
> +    if (!backend->size) {
> +        error_setg(errp, "can't create backend with size 0");
> +        return;
> +    }
> +
> +    path = object_get_canonical_path_component(OBJECT(backend));
> +    memory_region_init_ram(&backend->mr, OBJECT(backend), path,

Passing the full canonical path as the name of memory region is
redundant as that information is already passed via the owner
argument. It should just be a shorthand.

> +                           backend->size);
> +    g_free(path);
> +}
> +
> +static void
> +ram_backend_class_init(ObjectClass *oc, void *data)
> +{
> +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> +
> +    ucc->complete = ram_backend_memory_init;
> +}
> +
> +static const TypeInfo ram_backend_info = {
> +    .name = TYPE_MEMORY_BACKEND_RAM,
> +    .parent = TYPE_MEMORY_BACKEND,
> +    .class_init = ram_backend_class_init,
> +};
> +
> +static void register_types(void)
> +{
> +    type_register_static(&ram_backend_info);
> +}
> +
> +type_init(register_types);
> diff --git a/backends/hostmem.c b/backends/hostmem.c
> new file mode 100644
> index 0000000..8a34b0f
> --- /dev/null
> +++ b/backends/hostmem.c
> @@ -0,0 +1,113 @@
> +/*
> + * QEMU Host Memory Backend
> + *
> + * Copyright (C) 2013 Red Hat Inc
> + *
> + * Authors:
> + *   Igor Mammedov <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#include "sysemu/hostmem.h"
> +#include "sysemu/sysemu.h"
> +#include "qapi/visitor.h"
> +#include "qapi/qmp/qerror.h"
> +#include "qemu/config-file.h"
> +#include "qom/object_interfaces.h"
> +
> +static void
> +hostmemory_backend_get_size(Object *obj, Visitor *v, void *opaque,
> +                            const char *name, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> +    uint64_t value = backend->size;
> +
> +    visit_type_size(v, &value, name, errp);
> +}
> +
> +static void
> +hostmemory_backend_set_size(Object *obj, Visitor *v, void *opaque,
> +                            const char *name, Error **errp)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> +    Error *local_err = NULL;
> +    uint64_t value;
> +
> +    if (memory_region_size(&backend->mr)) {
> +        error_setg(&local_err, "cannot change property value\n");
> +        goto out;
> +    }
> +
> +    visit_type_size(v, &value, name, errp);
> +    if (local_err) {
> +        goto out;
> +    }
> +    if (!value) {
> +        error_setg(&local_err, "Property '%s.%s' doesn't take value '%"
> +                   PRIu64 "'", object_get_typename(obj), name , value);
> +        goto out;
> +    }
> +    backend->size = value;
> +out:
> +    error_propagate(errp, local_err);
> +}
> +
> +static void hostmemory_backend_initfn(Object *obj)

can you just call this _init and ..

> +{
> +    object_property_add(obj, "size", "int",
> +                        hostmemory_backend_get_size,
> +                        hostmemory_backend_set_size, NULL, NULL, NULL);
> +}
> +
> +static void hostmemory_backend_finalize(Object *obj)
> +{
> +    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
> +
> +    if (memory_region_size(&backend->mr)) {
> +        memory_region_destroy(&backend->mr);
> +    }
> +}
> +
> +static void
> +hostmemory_backend_memory_init(UserCreatable *uc, Error **errp)

And this becomes "_complete" for naming consistency?

> +{
> +    error_setg(errp, "memory_init is not implemented for type [%s]",
> +               object_get_typename(OBJECT(uc)));

What if complete for the concrete class is a genuine NOP? I think
that's for the child class decide. All this check is doing is
mandating that the child does "something" without any form of validity
checking. I would just drop it completely.

Regards,
Peter

> +}
> +
> +MemoryRegion *
> +host_memory_backend_get_memory(HostMemoryBackend *backend, Error **errp)
> +{
> +    return memory_region_size(&backend->mr) ? &backend->mr : NULL;
> +}
> +
> +static void
> +hostmemory_backend_class_init(ObjectClass *oc, void *data)
> +{
> +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> +
> +    ucc->complete = hostmemory_backend_memory_init;
> +}
> +
> +static const TypeInfo hostmemory_backend_info = {
> +    .name = TYPE_MEMORY_BACKEND,
> +    .parent = TYPE_OBJECT,
> +    .abstract = true,
> +    .class_size = sizeof(HostMemoryBackendClass),
> +    .class_init = hostmemory_backend_class_init,
> +    .instance_size = sizeof(HostMemoryBackend),
> +    .instance_init = hostmemory_backend_initfn,
> +    .instance_finalize = hostmemory_backend_finalize,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +static void register_types(void)
> +{
> +    type_register_static(&hostmemory_backend_info);
> +}
> +
> +type_init(register_types);
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> new file mode 100644
> index 0000000..bc3ffb3
> --- /dev/null
> +++ b/include/sysemu/hostmem.h
> @@ -0,0 +1,60 @@
> +/*
> + * QEMU Host Memory Backend
> + *
> + * Copyright (C) 2013 Red Hat Inc
> + *
> + * Authors:
> + *   Igor Mammedov <address@hidden>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#ifndef QEMU_RAM_H
> +#define QEMU_RAM_H
> +
> +#include "qom/object.h"
> +#include "qapi/error.h"
> +#include "exec/memory.h"
> +#include "qemu/option.h"
> +
> +#define TYPE_MEMORY_BACKEND "memory"
> +#define MEMORY_BACKEND(obj) \
> +    OBJECT_CHECK(HostMemoryBackend, (obj), TYPE_MEMORY_BACKEND)
> +#define MEMORY_BACKEND_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(HostMemoryBackendClass, (obj), TYPE_MEMORY_BACKEND)
> +#define MEMORY_BACKEND_CLASS(klass) \
> +    OBJECT_CLASS_CHECK(HostMemoryBackendClass, (klass), TYPE_MEMORY_BACKEND)
> +
> +typedef struct HostMemoryBackend HostMemoryBackend;
> +typedef struct HostMemoryBackendClass HostMemoryBackendClass;
> +
> +/**
> + * HostMemoryBackendClass:
> + * @parent_class: opaque parent class container
> + */
> +struct HostMemoryBackendClass {
> +    ObjectClass parent_class;
> +};
> +
> +/**
> + * @HostMemoryBackend
> + *
> + * @parent: opaque parent object container
> + * @size: amount of memory backend provides
> + * @id: unique identification string in memdev namespace
> + * @mr: MemoryRegion representing host memory belonging to backend
> + */
> +struct HostMemoryBackend {
> +    /* private */
> +    Object parent;
> +
> +    /* protected */
> +    uint64_t size;
> +
> +    MemoryRegion mr;
> +};
> +
> +MemoryRegion *host_memory_backend_get_memory(HostMemoryBackend *backend,
> +                                             Error **errp);
> +
> +#endif
> --
> 1.7.1
>
>