meson: Reject 32-bit hosts

32-bit hosts have been deprecated since 10.0.
As the first step, disable any such at configuration time.
Further patches will remove the dead code.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

docs/about/deprecated.rst

@@ -186,28 +186,6 @@ maintain our cross-compilation CI tests of the architecture. As we no longer
 have CI coverage support may bitrot away before the deprecation process
 completes.
 
-System emulation on 32-bit x86 hosts (since 8.0)
-''''''''''''''''''''''''''''''''''''''''''''''''
-
-Support for 32-bit x86 host deployments is increasingly uncommon in mainstream
-OS distributions given the widespread availability of 64-bit x86 hardware.
-The QEMU project no longer considers 32-bit x86 support for system emulation to
-be an effective use of its limited resources, and thus intends to discontinue
-it. Since all recent x86 hardware from the past >10 years is capable of the
-64-bit x86 extensions, a corresponding 64-bit OS should be used instead.
-
-TCG Plugin support not enabled by default on 32-bit hosts (since 9.2)
-'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
-
-While it is still possible to enable TCG plugin support for 32-bit
-hosts there are a number of potential pitfalls when instrumenting
-64-bit guests. The plugin APIs typically pass most addresses as
-uint64_t but practices like encoding that address in a host pointer
-for passing as user-data will lose data. As most software analysis
-benefits from having plenty of host memory it seems reasonable to
-encourage users to use 64 bit builds of QEMU for analysis work
-whatever targets they are instrumenting.
-
 TCG Plugin support not enabled by default with TCI (since 9.2)
 ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
 
@@ -216,13 +194,6 @@ is going to be so much slower it wouldn't make sense for any serious
 instrumentation. Due to implementation differences there will also be
 anomalies in things like memory instrumentation.
 
-32-bit host operating systems (since 10.0)
-''''''''''''''''''''''''''''''''''''''''''
-
-Keeping 32-bit host support alive is a substantial burden for the
-QEMU project.  Thus QEMU will in future drop the support for all
-32-bit host systems.
-
 System emulator CPUs
 --------------------
 

docs/about/removed-features.rst

@@ -572,6 +572,12 @@ like the ``akita`` or ``terrier``; it has been deprecated in the
 kernel since 2001. None of the board types QEMU supports need
 ``param_struct`` support, so this option has been removed.
 
+32-bit host operating systems (removed in 11.0)
+'''''''''''''''''''''''''''''''''''''''''''''''
+
+Keeping 32-bit host support alive was a substantial burden for the
+QEMU project.  Thus QEMU dropped all support for all 32-bit host systems.
+
 
 User-mode emulator command line arguments
 -----------------------------------------

meson.build

@@ -332,6 +332,10 @@ endif
 # Compiler flags #
 ##################
 
+if cc.sizeof('void *') < 8
+  error('QEMU requires a 64-bit CPU host architecture')
+endif
+
 foreach lang : all_languages
   compiler = meson.get_compiler(lang)
   if compiler.get_id() == 'gcc' and compiler.version().version_compare('>=7.4')
@@ -3247,9 +3251,6 @@ if host_os == 'windows'
   endif
 endif
 
-# Detect host pointer size for the target configuration loop.
-host_long_bits = cc.sizeof('void *') * 8
-
 # Detect if ConvertStringToBSTR has been defined in _com_util namespace
 if host_os == 'windows'
   has_convert_string_to_bstr = cxx.links('''
@@ -3360,10 +3361,6 @@ foreach target : target_dirs
 
   target_kconfig = []
   foreach sym: accelerators
-    # Disallow 64-bit on 32-bit emulation and virtualization
-    if host_long_bits < config_target['TARGET_LONG_BITS'].to_int()
-      continue
-    endif
     if sym == 'CONFIG_TCG' or target in accelerator_targets.get(sym, [])
       config_target += { sym: 'y' }
       config_all_accel += { sym: 'y' }
@@ -5036,12 +5033,6 @@ if host_arch == 'unknown'
     message('configure has succeeded and you can continue to build, but')
     message('QEMU will use a slow interpreter to emulate the target CPU.')
   endif
-elif host_long_bits < 64
-  message()
-  warning('DEPRECATED HOST CPU')
-  message()
-  message('Support for 32-bit CPU host architecture ' + cpu + ' is going')
-  message('to be dropped in a future QEMU release.')
 elif host_arch == 'mips'
   message()
   warning('DEPRECATED HOST CPU')