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+=================
+VMCoreInfo device
+=================
+
+The ``-device vmcoreinfo`` will create a ``fw_cfg`` entry for a guest to
+store dump details.
+
+``etc/vmcoreinfo``
+==================
+
+A guest may use this ``fw_cfg`` entry to add information details to QEMU
+dumps.
+
+The entry of 16 bytes has the following layout, in little-endian::
+
+    #define VMCOREINFO_FORMAT_NONE 0x0
+    #define VMCOREINFO_FORMAT_ELF 0x1
+
+    struct FWCfgVMCoreInfo {
+        uint16_t host_format;  /* formats host supports */
+        uint16_t guest_format; /* format guest supplies */
+        uint32_t size;         /* size of vmcoreinfo region */
+        uint64_t paddr;        /* physical address of vmcoreinfo region */
+    };
+
+Only full write (of 16 bytes) are considered valid for further
+processing of entry values.
+
+A write of 0 in ``guest_format`` will disable further processing of
+vmcoreinfo entry values & content.
+
+You may write a ``guest_format`` that is not supported by the host, in
+which case the entry data can be ignored by QEMU (but you may still
+access it through a debugger, via ``vmcoreinfo_realize::vmcoreinfo_state``).
+
+Format & content
+================
+
+As of QEMU 2.11, only ``VMCOREINFO_FORMAT_ELF`` is supported.
+
+The entry gives location and size of an ELF note that is appended in
+qemu dumps.
+
+The note format/class must be of the target bitness and the size must
+be less than 1Mb.
+
+If the ELF note name is ``VMCOREINFO``, it is expected to be the Linux
+vmcoreinfo note (see `the kernel documentation for its format
+<https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-kernel-vmcoreinfo>`_).
+In this case, qemu dump code will read the content
+as a key=value text file, looking for ``NUMBER(phys_base)`` key
+value. The value is expected to be more accurate than architecture
+guess of the value. This is useful for KASLR-enabled guest with
+ancient tools not handling the ``VMCOREINFO`` note.