hw/misc: add vmcoreinfo device

See docs/specs/vmcoreinfo.txt for details.

"etc/vmcoreinfo" fw_cfg entry is added when using "-device vmcoreinfo".

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/docs/specs/vmcoreinfo.txt b/docs/specs/vmcoreinfo.txt
new file mode 100644
index 0000000000..2868a77142
--- /dev/null
+++ b/docs/specs/vmcoreinfo.txt
@@ -0,0 +1,41 @@
+=================
+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.