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docs/specs/vmcoreinfo: Convert to rST

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Convert docs/specs/vmcoreinfo.txt to rST format.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20230927151205.70930-8-peter.maydell@linaro.org
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
This commit is contained in:
Peter Maydell 2023-09-27 16:12:04 +01:00
parent 6e0c849275
commit 096d3ce231
4 changed files with 56 additions and 53 deletions
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1
MAINTAINERS
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@ -2884,6 +2884,7 @@ F: include/sysemu/dump.h
F: qapi/dump.json
F: scripts/dump-guest-memory.py
F: stubs/dump.c
F: docs/specs/vmcoreinfo.rst
Error reporting
M: Markus Armbruster <armbru@redhat.com>

1
docs/specs/index.rst
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@ -30,3 +30,4 @@ guest hardware that is specific to QEMU.
pvpanic
standard-vga
virt-ctlr
vmcoreinfo

54
docs/specs/vmcoreinfo.rst Normal file
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@ -0,0 +1,54 @@
=================
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.

53
docs/specs/vmcoreinfo.txt
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@ -1,53 +0,0 @@
=================
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 Documentation/ABI/testing/sysfs-kernel-vmcoreinfo
in Linux source). 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.