Merge remote-tracking branch 'remotes/ehabkost/tags/machine-next-pull-request' into staging

Machine and x86 queue, 2019-07-05

* CPU die topology support (Like Xu)
* Deprecation of features (Igor Mammedov):
  * 'mem' parameter of '-numa node' option
  * implict memory distribution between NUMA nodes
  * deprecate -mem-path fallback to anonymous RAM
* x86 versioned CPU models (Eduardo Habkost)
* SnowRidge CPU model (Paul Lai)
* Add deprecation information to query-machines (Eduardo Habkost)
* Other i386 fixes

# gpg: Signature made Fri 05 Jul 2019 23:12:09 BST
# gpg:                using RSA key 5A322FD5ABC4D3DBACCFD1AA2807936F984DC5A6
# gpg:                issuer "ehabkost@redhat.com"
# gpg: Good signature from "Eduardo Habkost <ehabkost@redhat.com>" [full]
# Primary key fingerprint: 5A32 2FD5 ABC4 D3DB ACCF  D1AA 2807 936F 984D C5A6

* remotes/ehabkost/tags/machine-next-pull-request: (42 commits)
  tests: use -numa memdev option in tests instead of legacy 'mem' option
  numa: allow memory-less nodes when using memdev as backend
  numa: Make deprecation warnings conditional on !qtest_enabled()
  i386: Add Cascadelake-Server-v2 CPU model
  docs: Deprecate CPU model runnability guarantees
  i386: Make unversioned CPU models be aliases
  i386: Replace -noTSX, -IBRS, -IBPB CPU models with aliases
  i386: Define -IBRS, -noTSX, -IBRS versions of CPU models
  i386: Register versioned CPU models
  i386: Get model-id from CPU object on "-cpu help"
  i386: Add x-force-features option for testing
  qmp: Add "alias-of" field to query-cpu-definitions
  i386: Introduce SnowRidge CPU model
  qmp: Add deprecation information to query-machines
  vl.c: Add -smp, dies=* command line support and update doc
  machine: Refactor smp_parse() in vl.c as MachineClass::smp_parse()
  target/i386: Add CPUID.1F generation support for multi-dies PCMachine
  i386: Remove unused host_cpudef variable
  x86/cpu: use FeatureWordArray to define filtered_features
  i386: make 'hv-spinlocks' a regular uint32 property
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 40c017b..c90b08d 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -88,6 +88,39 @@ The @code{-realtime mlock=on|off} argument has been replaced by the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.
+
 @section QEMU Machine Protocol (QMP) commands
 
 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
@@ -259,3 +292,22 @@ 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.