=================
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.

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.