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75e2cb1441
shm can surely serve as the shared memory for coco-VMs. But currently it doesn't check the backend->guest_memfd to pass down the RAM_GUEST_MEMFD flag. It leads to failure when creating coco-VMs (e.g., TDX guest) which require private mmeory. Set and pass down RAM_GUEST_MEMFD when backend->guest_memfd is true, to allow shm memory backend serve as shared memory for coco-VMs. Cc: Stefano Garzarella <sgarzare@redhat.com> Cc: qemu-stable <qemu-stable@nongnu.org> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Stefano Garzarella <sgarzare@redhat.com> Link: https://lore.kernel.org/r/20250721065220.895606-1-xiaoyao.li@intel.com Signed-off-by: Peter Xu <peterx@redhat.com>
94 lines
2.3 KiB
C
94 lines
2.3 KiB
C
/*
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* QEMU host POSIX shared memory object backend
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*
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* Copyright (C) 2024 Red Hat Inc
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*
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* Authors:
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* Stefano Garzarella <sgarzare@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "system/hostmem.h"
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#include "qapi/error.h"
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#include "migration/cpr.h"
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#define TYPE_MEMORY_BACKEND_SHM "memory-backend-shm"
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OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendShm, MEMORY_BACKEND_SHM)
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struct HostMemoryBackendShm {
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HostMemoryBackend parent_obj;
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};
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static bool
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shm_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
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{
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g_autofree char *backend_name = host_memory_backend_get_name(backend);
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uint32_t ram_flags;
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int fd = cpr_find_fd(backend_name, 0);
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if (!backend->size) {
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error_setg(errp, "can't create shm backend with size 0");
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return false;
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}
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if (!backend->share) {
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error_setg(errp, "can't create shm backend with `share=off`");
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return false;
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}
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if (fd >= 0) {
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goto have_fd;
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}
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fd = qemu_shm_alloc(backend->size, errp);
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if (fd < 0) {
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return false;
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}
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cpr_save_fd(backend_name, 0, fd);
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have_fd:
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/* Let's do the same as memory-backend-ram,share=on would do. */
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ram_flags = RAM_SHARED;
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ram_flags |= backend->reserve ? 0 : RAM_NORESERVE;
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ram_flags |= backend->guest_memfd ? RAM_GUEST_MEMFD : 0;
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return memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend),
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backend_name, backend->size,
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ram_flags, fd, 0, errp);
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}
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static void
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shm_backend_instance_init(Object *obj)
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{
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HostMemoryBackendShm *m = MEMORY_BACKEND_SHM(obj);
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MEMORY_BACKEND(m)->share = true;
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}
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static void
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shm_backend_class_init(ObjectClass *oc, const void *data)
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{
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HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
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bc->alloc = shm_backend_memory_alloc;
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}
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static const TypeInfo shm_backend_info = {
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.name = TYPE_MEMORY_BACKEND_SHM,
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.parent = TYPE_MEMORY_BACKEND,
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.instance_init = shm_backend_instance_init,
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.class_init = shm_backend_class_init,
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.instance_size = sizeof(HostMemoryBackendShm),
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};
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static void register_types(void)
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{
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type_register_static(&shm_backend_info);
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}
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type_init(register_types);
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