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[Qemu-devel] [PULL 39/47] Add memfd based hostmem
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 39/47] Add memfd based hostmem |
Date: |
Mon, 5 Feb 2018 20:28:53 +0100 |
From: Marc-André Lureau <address@hidden>
Add a new memory backend, similar to hostmem-file, except that it
doesn't need to create files. It also enforces memory sealing.
This backend is mainly useful for sharing the memory with other
processes.
Note that Linux supports transparent huge-pages of shmem/memfd memory
since 4.8. It is relatively easier to set up THP than a dedicate
hugepage mount point by using "madvise" in
/sys/kernel/mm/transparent_hugepage/shmem_enabled.
Since 4.14, memfd allows to set hugetlb requirement explicitly.
Pending for merge in 4.16 is memfd sealing support for hugetlb backed
memory.
Usage:
-object memory-backend-memfd,id=mem1,size=1G
Signed-off-by: Marc-André Lureau <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
backends/Makefile.objs | 2 +
backends/hostmem-memfd.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++
qemu-options.hx | 22 ++++++
3 files changed, 194 insertions(+)
create mode 100644 backends/hostmem-memfd.c
diff --git a/backends/Makefile.objs b/backends/Makefile.objs
index 0400799..67eeeba 100644
--- a/backends/Makefile.objs
+++ b/backends/Makefile.objs
@@ -8,3 +8,5 @@ common-obj-$(CONFIG_LINUX) += hostmem-file.o
common-obj-y += cryptodev.o
common-obj-y += cryptodev-builtin.o
+
+common-obj-$(CONFIG_LINUX) += hostmem-memfd.o
diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c
new file mode 100644
index 0000000..1e20fe0
--- /dev/null
+++ b/backends/hostmem-memfd.c
@@ -0,0 +1,170 @@
+/*
+ * QEMU host memfd memory backend
+ *
+ * Copyright (C) 2018 Red Hat Inc
+ *
+ * Authors:
+ * Marc-André Lureau <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 "qemu/osdep.h"
+#include "qemu-common.h"
+#include "sysemu/hostmem.h"
+#include "sysemu/sysemu.h"
+#include "qom/object_interfaces.h"
+#include "qemu/memfd.h"
+#include "qapi/error.h"
+
+#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
+
+#define MEMORY_BACKEND_MEMFD(obj) \
+ OBJECT_CHECK(HostMemoryBackendMemfd, (obj), TYPE_MEMORY_BACKEND_MEMFD)
+
+typedef struct HostMemoryBackendMemfd HostMemoryBackendMemfd;
+
+struct HostMemoryBackendMemfd {
+ HostMemoryBackend parent_obj;
+
+ bool hugetlb;
+ uint64_t hugetlbsize;
+ bool seal;
+};
+
+static void
+memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(backend);
+ char *name;
+ int fd;
+
+ if (!backend->size) {
+ error_setg(errp, "can't create backend with size 0");
+ return;
+ }
+
+ if (host_memory_backend_mr_inited(backend)) {
+ return;
+ }
+
+ backend->force_prealloc = mem_prealloc;
+ fd = qemu_memfd_create(TYPE_MEMORY_BACKEND_MEMFD, backend->size,
+ m->hugetlb, m->hugetlbsize, m->seal ?
+ F_SEAL_GROW | F_SEAL_SHRINK | F_SEAL_SEAL : 0,
+ errp);
+ if (fd == -1) {
+ return;
+ }
+
+ name = object_get_canonical_path(OBJECT(backend));
+ memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
+ name, backend->size, true, fd, errp);
+ g_free(name);
+}
+
+static bool
+memfd_backend_get_hugetlb(Object *o, Error **errp)
+{
+ return MEMORY_BACKEND_MEMFD(o)->hugetlb;
+}
+
+static void
+memfd_backend_set_hugetlb(Object *o, bool value, Error **errp)
+{
+ MEMORY_BACKEND_MEMFD(o)->hugetlb = value;
+}
+
+static void
+memfd_backend_set_hugetlbsize(Object *obj, Visitor *v, const char *name,
+ void *opaque, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+ Error *local_err = NULL;
+ uint64_t value;
+
+ if (host_memory_backend_mr_inited(MEMORY_BACKEND(obj))) {
+ error_setg(&local_err, "cannot change property value");
+ goto out;
+ }
+
+ visit_type_size(v, name, &value, &local_err);
+ 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;
+ }
+ m->hugetlbsize = value;
+out:
+ error_propagate(errp, local_err);
+}
+
+static void
+memfd_backend_get_hugetlbsize(Object *obj, Visitor *v, const char *name,
+ void *opaque, Error **errp)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+ uint64_t value = m->hugetlbsize;
+
+ visit_type_size(v, name, &value, errp);
+}
+
+static bool
+memfd_backend_get_seal(Object *o, Error **errp)
+{
+ return MEMORY_BACKEND_MEMFD(o)->seal;
+}
+
+static void
+memfd_backend_set_seal(Object *o, bool value, Error **errp)
+{
+ MEMORY_BACKEND_MEMFD(o)->seal = value;
+}
+
+static void
+memfd_backend_instance_init(Object *obj)
+{
+ HostMemoryBackendMemfd *m = MEMORY_BACKEND_MEMFD(obj);
+
+ /* default to sealed file */
+ m->seal = true;
+}
+
+static void
+memfd_backend_class_init(ObjectClass *oc, void *data)
+{
+ HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
+
+ bc->alloc = memfd_backend_memory_alloc;
+
+ object_class_property_add_bool(oc, "hugetlb",
+ memfd_backend_get_hugetlb,
+ memfd_backend_set_hugetlb,
+ &error_abort);
+ object_class_property_add(oc, "hugetlbsize", "int",
+ memfd_backend_get_hugetlbsize,
+ memfd_backend_set_hugetlbsize,
+ NULL, NULL, &error_abort);
+ object_class_property_add_bool(oc, "seal",
+ memfd_backend_get_seal,
+ memfd_backend_set_seal,
+ &error_abort);
+}
+
+static const TypeInfo memfd_backend_info = {
+ .name = TYPE_MEMORY_BACKEND_MEMFD,
+ .parent = TYPE_MEMORY_BACKEND,
+ .instance_init = memfd_backend_instance_init,
+ .class_init = memfd_backend_class_init,
+ .instance_size = sizeof(HostMemoryBackendMemfd),
+};
+
+static void register_types(void)
+{
+ type_register_static(&memfd_backend_info);
+}
+
+type_init(register_types);
diff --git a/qemu-options.hx b/qemu-options.hx
index 8ce427d..265cf9f 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4024,6 +4024,28 @@ Memory backend objects offer more control than the
@option{-m} option that is
traditionally used to define guest RAM. Please refer to
@option{memory-backend-file} for a description of the options.
address@hidden -object
memory-backend-memfd,address@hidden,address@hidden|off},address@hidden|off},address@hidden|off},address@hidden,address@hidden,address@hidden|preferred|bind|interleave},address@hidden|off},address@hidden|off},address@hidden
+
+Creates an anonymous memory file backend object, which allows QEMU to
+share the memory with an external process (e.g. when using
+vhost-user). The memory is allocated with memfd and optional
+sealing. (Linux only)
+
+The @option{seal} option creates a sealed-file, that will block
+further resizing the memory ('on' by default).
+
+The @option{hugetlb} option specify the file to be created resides in
+the hugetlbfs filesystem (since Linux 4.14). Used in conjunction with
+the @option{hugetlb} option, the @option{hugetlbsize} option specify
+the hugetlb page size on systems that support multiple hugetlb page
+sizes (it must be a power of 2 value supported by the system).
+
+In some versions of Linux, the @option{hugetlb} option is incompatible
+with the @option{seal} option (requires at least Linux 4.16).
+
+Please refer to @option{memory-backend-file} for a description of the
+other options.
+
@item -object rng-random,address@hidden,address@hidden/dev/random}
Creates a random number generator backend which obtains entropy from
--
1.8.3.1
- [Qemu-devel] [PULL 26/47] ivshmem: Don't update non-existent MSI routes, (continued)
- [Qemu-devel] [PULL 26/47] ivshmem: Don't update non-existent MSI routes, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 35/47] cpus: join thread when removing a vCPU, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 34/47] cpus: hvf: unregister thread with RCU, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 33/47] cpus: tcg: unregister thread with RCU, fix exiting of loop on unplug, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 36/47] memfd: add error argument, instead of perror(), Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 38/47] memfd: add hugetlbsize argument, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 37/47] memfd: add hugetlb support, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 40/47] tests: keep compiling failing vhost-user tests, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 44/47] Add the Windows Hypervisor Platform accelerator., Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 43/47] tests/test-filter-redirector: move close(), Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 39/47] Add memfd based hostmem,
Paolo Bonzini <=
- [Qemu-devel] [PULL 41/47] vhost-user-test: make read-guest-mem setup its own qemu, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 42/47] tests: use memfd in vhost-user-test, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 45/47] Add the WHPX vcpu API, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 47/47] Add the WHPX acceleration enlightenments, Paolo Bonzini, 2018/02/05
- [Qemu-devel] [PULL 46/47] Introduce the WHPX impl, Paolo Bonzini, 2018/02/05
- Re: [Qemu-devel] [PULL 00/47] Misc patches for 2018-02-05, Peter Maydell, 2018/02/06