migration: rename migration_bitmap_sync_range to ramblock_sync_dirty_bitmap

[mirror_qemu.git] / qemu-deprecated.texi

diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 40c017b4265959c102aa866044f777d78eaaf123..fff07bb2a3199970ce398dd097d083ebb8d0c3e1 100644 (file)
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -88,6 +88,59 @@ The @code{-realtime mlock=on|off} argument has been replaced by the
 The ``-virtfs_synth'' argument is now deprecated. Please use ``-fsdev synth''
 and ``-device virtio-9p-...'' instead.
 
+@subsection -numa node,mem=@var{size} (since 4.1)
+
+The parameter @option{mem} of @option{-numa node} is used to assign a part of
+guest RAM to a NUMA node. But when using it, it's impossible to manage specified
+RAM chunk on the host side (like bind it to a host node, setting bind policy, ...),
+so guest end-ups with the fake NUMA configuration with suboptiomal performance.
+However since 2014 there is an alternative way to assign RAM to a NUMA node
+using parameter @option{memdev}, which does the same as @option{mem} and adds
+means to actualy manage node RAM on the host side. Use parameter @option{memdev}
+with @var{memory-backend-ram} backend as an replacement for parameter @option{mem}
+to achieve the same fake NUMA effect or a properly configured
+@var{memory-backend-file} backend to actually benefit from NUMA configuration.
+In future new machine versions will not accept the option but it will still
+work with old machine types. User can check QAPI schema to see if the legacy
+option is supported by looking at MachineInfo::numa-mem-supported property.
+
+@subsection -numa node (without memory specified) (since 4.1)
+
+Splitting RAM by default between NUMA nodes has the same issues as @option{mem}
+parameter described above with the difference that the role of the user plays
+QEMU using implicit generic or board specific splitting rule.
+Use @option{memdev} with @var{memory-backend-ram} backend or @option{mem} (if
+it's supported by used machine type) to define mapping explictly instead.
+
+@subsection -mem-path fallback to RAM (since 4.1)
+Currently if guest RAM allocation from file pointed by @option{mem-path}
+fails, QEMU falls back to allocating from RAM, which might result
+in unpredictable behavior since the backing file specified by the user
+is ignored. In the future, users will be responsible for making sure
+the backing storage specified with @option{-mem-path} can actually provide
+the guest RAM configured with @option{-m} and QEMU will fail to start up if
+RAM allocation is unsuccessful.
+
+@subsection RISC-V -bios (since 4.1)
+
+QEMU 4.1 introduced support for the -bios option in QEMU for RISC-V for the
+RISC-V virt machine and sifive_u machine.
+
+QEMU 4.1 has no changes to the default behaviour to avoid breakages. This
+default will change in a future QEMU release, so please prepare now. All users
+of the virt or sifive_u machine must change their command line usage.
+
+QEMU 4.1 has three options, please migrate to one of these three:
+ 1. ``-bios none`` - This is the current default behavior if no -bios option
+      is included. QEMU will not automatically load any firmware. It is up
+      to the user to load all the images they need.
+ 2. ``-bios default`` - In a future QEMU release this will become the default
+      behaviour if no -bios option is specified. This option will load the
+      default OpenSBI firmware automatically. The firmware is included with
+      the QEMU release and no user interaction is required. All a user needs
+      to do is specify the kernel they want to boot with the -kernel option
+ 3. ``-bios <file>`` - Tells QEMU to load the specified file as the firmwrae.
+
 @section QEMU Machine Protocol (QMP) commands
 
 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
@@ -259,3 +312,22 @@ subset of the image.
 In the future, QEMU will require Python 3 to be available at
 build time.  Support for Python 2 in scripts shipped with QEMU
 is deprecated.
+
+@section Backwards compatibility
+
+@subsection Runnability guarantee of CPU models (since 4.1.0)
+
+Previous versions of QEMU never changed existing CPU models in
+ways that introduced additional host software or hardware
+requirements to the VM.  This allowed management software to
+safely change the machine type of an existing VM without
+introducing new requirements ("runnability guarantee").  This
+prevented CPU models from being updated to include CPU
+vulnerability mitigations, leaving guests vulnerable in the
+default configuration.
+
+The CPU model runnability guarantee won't apply anymore to
+existing CPU models.  Management software that needs runnability
+guarantees must resolve the CPU model aliases using te
+``alias-of'' field returned by the ``query-cpu-definitions'' QMP
+command.