Merge tag 'mem-2023-10-12' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support memory devices with multiple memslots
- Support memory devices that dynamically consume memslots
- Support memory devices that can automatically decide on the number of
  memslots to use
- virtio-mem support for exposing memory dynamically via multiple
  memslots
- Some required cleanups/refactorings

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# gpg: Signature made Thu 12 Oct 2023 09:49:39 EDT
# gpg:                using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
# gpg:                issuer "david@redhat.com"
# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg:                 aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg:                 aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D  FCCA 4DDE 10F7 00FF 835A

* tag 'mem-2023-10-12' of https://github.com/davidhildenbrand/qemu:
  virtio-mem: Mark memslot alias memory regions unmergeable
  memory,vhost: Allow for marking memory device memory regions unmergeable
  virtio-mem: Expose device memory dynamically via multiple memslots if enabled
  virtio-mem: Update state to match bitmap as soon as it's been migrated
  virtio-mem: Pass non-const VirtIOMEM via virtio_mem_range_cb
  memory: Clarify mapping requirements for RamDiscardManager
  memory-device,vhost: Support automatic decision on the number of memslots
  vhost: Add vhost_get_max_memslots()
  kvm: Add stub for kvm_get_max_memslots()
  memory-device,vhost: Support memory devices that dynamically consume memslots
  memory-device: Track required and actually used memslots in DeviceMemoryState
  stubs: Rename qmp_memory_device.c to memory_device.c
  memory-device: Support memory devices with multiple memslots
  vhost: Return number of free memslots
  kvm: Return number of free memslots
  softmmu/physmem: Fixup qemu_ram_block_from_host() documentation
  vhost: Remove vhost_backend_can_merge() callback
  vhost: Rework memslot filtering and fix "used_memslot" tracking

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 605b160a7e..30c376a4de 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -83,6 +83,21 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length);
 ram_addr_t qemu_ram_addr_from_host(void *ptr);
 ram_addr_t qemu_ram_addr_from_host_nofail(void *ptr);
 RAMBlock *qemu_ram_block_by_name(const char *name);
+
+/*
+ * Translates a host ptr back to a RAMBlock and an offset in that RAMBlock.
+ *
+ * @ptr: The host pointer to translate.
+ * @round_offset: Whether to round the result offset down to a target page
+ * @offset: Will be set to the offset within the returned RAMBlock.
+ *
+ * Returns: RAMBlock (or NULL if not found)
+ *
+ * By the time this function returns, the returned pointer is not protected
+ * by RCU anymore.  If the caller is not within an RCU critical section and
+ * does not hold the iothread lock, it must have other means of protecting the
+ * pointer, such as a reference to the memory region that owns the RAMBlock.
+ */
 RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
                                    ram_addr_t *offset);
 ram_addr_t qemu_ram_block_host_offset(RAMBlock *rb, void *host);