More precisely, the "x-file-slots" count is bumped for all machine types
that:
(a) use fw_cfg, and
(b) are not versioned (hence migration is not expected to work for them
    across QEMU releases anyway), or have version 2.9.

This affects machine types implemented in the following source files:

- "hw/arm/virt.c". The "virt-*" machine type is versioned, and the <= 2.8
  versions already depend on HW_COMPAT_2_8 (see commit e353aac5).
  Therefore adding the "x-file-slots" compat values to HW_COMPAT_2_8
  suffices.

- "hw/i386/pc.c". The "pc-i440fx-*" (including "pc-*") and "pc-q35-*"
  machine types are versioned. Modifying HW_COMPAT_2_8 is sufficient here
  too (see commit "pc: Add 2.9 machine-types"). The "isapc" machtype is
  not versioned. The "xenfv" machine type, which uses fw_cfg for direct
  kernel booting, is also not versioned.

- "hw/ppc/mac_newworld.c". The "mac99" machine type is not versioned.

- "hw/ppc/mac_oldworld.c". The "g3beige" machine type is not versioned.

- "hw/sparc/sun4m.c". None of the 9 machine types defined in this file
  appear versioned.

- "hw/sparc64/sun4u.c". None of the 3 machine types defined in this file
  appear versioned.

Cc: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alexander Graf <agraf@suse.de>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Artyom Tarasenko <atar4qemu@gmail.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Acked-by: NGabriel Somlo <somlo@cmu.edu>
Tested-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>

We'd like to raise the value of FW_CFG_FILE_SLOTS. Doing it naively could
lead to problems with backward migration: a more recent QEMU (running an
older machine type) would allow the guest, in fw_cfg_select(), to select a
high key value that is unavailable in the same machine type implemented by
the older (target) QEMU. On the target host, fw_cfg_data_read() for
example could dereference nonexistent entries.

As first step, size the FWCfgState.entries[*] and FWCfgState.entry_order
arrays dynamically. All three array sizes will be influenced by the new
field FWCfgState.file_slots (and matching device property).

Make the following changes:

- Replace the FW_CFG_FILE_SLOTS macro with FW_CFG_FILE_SLOTS_MIN (minimum
  count of fw_cfg file slots) in the header file. The value remains 0x10.

- Replace all uses of FW_CFG_FILE_SLOTS with a helper function called
  fw_cfg_file_slots(), returning the new property.

- Eliminate the macro FW_CFG_MAX_ENTRY, and replace all its uses with a
  helper function called fw_cfg_max_entry().

- In the MMIO- and IO-mapped realize functions both, allocate all three
  arrays dynamically, based on the new property.

- The new property defaults to FW_CFG_FILE_SLOTS_MIN. This is going to be
  customized in the following patches.

Cc: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Acked-by: NGabriel Somlo <somlo@cmu.edu>
Tested-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>

Useful to send guest data back to QEMU.

Changes from Laszlo Ersek <lersek@redhat.com>:
- rebase the patch from Michael Tsirkin's original postings at [1] and [2]
  to the following patches:
  - loader: Allow a custom AddressSpace when loading ROMs
  - loader: Add AddressSpace loading support to uImages
  - loader: fix handling of custom address spaces when adding ROM blobs
- reject such writes immediately that would exceed the end of the array,
  rather than performing a partial write before setting the error bit: see
  the (len != dma.length) condition
- document the write interface

[1] http://lists.nongnu.org/archive/html/qemu-devel/2016-02/msg04968.html
[2] http://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg02735.html

Cc: "Gabriel L. Somlo" <somlo@cmu.edu>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Michael Walle <michael@walle.cc>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Shannon Zhao <zhaoshenglong@huawei.com>
Cc: qemu-arm@nongnu.org
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NMarcel Apfelbaum <marcel@redhat.com>
Acked-by: NGabriel Somlo <somlo@cmu.edu>
Tested-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NEduardo Habkost <ehabkost@redhat.com>

FW CFG's primary user is QEMU, which uses it to expose configuration
information (in the widest sense) to Firmware.  Thus the name FW CFG.

FW CFG can also be used by others for their own purposes.  QEMU is
merely acting as transport then.  Names starting with opt/ are
reserved for such uses.  There is no provision, however, to guide safe
sharing among different such users.

Fix that, loosely following QMP precedence: names should start with
opt/RFQDN/, where RFQDN is a reverse fully qualified domain name you
control.

Based on a more ambitious patch from Michael Tsirkin.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Gabriel L. Somlo <somlo@cmu.edu>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>

Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NMarc Marí <markmb@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Message-id: 1455906029-25565-6-git-send-email-somlo@cmu.edu
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Move documentation for fw_cfg functions internal to qemufrom
docs/specs/fw_cfg.txt to the fw_cfg.h header file, next to
their prototype declarations, formatted as doc-comments.

NOTE: Documentation for fw_cfg_add_callback() is completely
dropped by this patch, as that function has been eliminated
by commit 023e3148.
Suggested-by: NPeter Maydell <peter.maydell@linaro.org>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc Marí <markmb@redhat.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Message-id: 1446733972-1602-2-git-send-email-somlo@cmu.edu
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Return a static signature ("QEMU CFG") if the guest does a read to the
DMA address io register.
Signed-off-by: NKevin O'Connor <kevin@koconnor.net>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Add fw_cfg DMA interface specification in the documentation.

Based on Gerd Hoffman's initial implementation.
Signed-off-by: NMarc Marí <markmb@redhat.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Document the behavior of fw_cfg_modify_iXX() for leak-less updating
of integer-type blobs.

Currently only fw_cfg_modify_i16() is coded, but 32- and 64-bit versions
may be added later if necessary..
Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Allow users to provide custom fw_cfg blobs with ascii string
payloads specified directly on the qemu command line.
Suggested-by: NJordan Justen <jordan.l.justen@intel.com>
Suggested-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Message-id: 1443544141-26568-1-git-send-email-somlo@cmu.edu
Reviewd-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Allow user supplied files to be inserted into the fw_cfg
device before starting the guest. Since fw_cfg_add_file()
already disallows duplicate fw_cfg file names, qemu will
exit with an error message if the user supplies multiple
blobs with the same fw_cfg file name, or if a blob name
collides with a fw_cfg name programmatically added from
within the QEMU source code. A warning message will be
printed if the fw_cfg item name does not begin with the
prefix "opt/", which is recommended for external, user
provided blobs.
Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

This document covers the guest-side hardware interface, as
well as the host-side programming API of QEMU's firmware
configuration (fw_cfg) device.
Signed-off-by: NJordan Justen <jordan.l.justen@intel.com>
Signed-off-by: NGabriel Somlo <somlo@cmu.edu>
Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>