accel: Add Meson and config support for MSHV accelerator

Introduce a Meson feature option and default-config entry to allow
building QEMU with MSHV (Microsoft Hypervisor) acceleration support.

This is the first step toward implementing an MSHV backend in QEMU.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Link: https://lore.kernel.org/r/20250916164847.77883-2-magnuskulke@linux.microsoft.com
[Add error for unavailable accelerator. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/Kconfig

@@ -13,6 +13,9 @@ config TCG
 config KVM
     bool
 
+config MSHV
+    bool
+
 config XEN
     bool
     select FSDEV_9P if VIRTFS

meson.build

@@ -334,6 +334,7 @@ elif cpu == 'x86_64'
     'CONFIG_HVF': ['x86_64-softmmu'],
     'CONFIG_NVMM': ['i386-softmmu', 'x86_64-softmmu'],
     'CONFIG_WHPX': ['i386-softmmu', 'x86_64-softmmu'],
+    'CONFIG_MSHV': ['x86_64-softmmu'],
   }
 endif
 
@@ -883,6 +884,14 @@ accelerators = []
 if get_option('kvm').allowed() and host_os == 'linux'
   accelerators += 'CONFIG_KVM'
 endif
+
+if get_option('mshv').allowed() and host_os == 'linux'
+  if get_option('mshv').enabled() and host_machine.cpu() != 'x86_64'
+    error('mshv accelerator requires x64_64 host')
+  endif
+  accelerators += 'CONFIG_MSHV'
+endif
+
 if get_option('whpx').allowed() and host_os == 'windows'
   if get_option('whpx').enabled() and host_machine.cpu() != 'x86_64'
     error('WHPX requires 64-bit host')
@@ -952,6 +961,9 @@ endif
 if 'CONFIG_WHPX' not in accelerators and get_option('whpx').enabled()
   error('WHPX not available on this platform')
 endif
+if 'CONFIG_MSHV' not in accelerators and get_option('mshv').enabled()
+  error('mshv not available on this platform')
+endif
 
 xen = not_found
 if get_option('xen').enabled() or (get_option('xen').auto() and have_system)
@@ -4827,6 +4839,7 @@ if have_system
   summary_info += {'HVF support':       config_all_accel.has_key('CONFIG_HVF')}
   summary_info += {'WHPX support':      config_all_accel.has_key('CONFIG_WHPX')}
   summary_info += {'NVMM support':      config_all_accel.has_key('CONFIG_NVMM')}
+  summary_info += {'MSHV support':      config_all_accel.has_key('CONFIG_MSHV')}
   summary_info += {'Xen support':       xen.found()}
   if xen.found()
     summary_info += {'xen ctrl version':  xen.version()}

meson_options.txt

@@ -71,6 +71,8 @@ option('malloc', type : 'combo', choices : ['system', 'tcmalloc', 'jemalloc'],
 
 option('kvm', type: 'feature', value: 'auto',
        description: 'KVM acceleration support')
+option('mshv', type: 'feature', value: 'auto',
+       description: 'MSHV acceleration support')
 option('whpx', type: 'feature', value: 'auto',
        description: 'WHPX acceleration support')
 option('hvf', type: 'feature', value: 'auto',

scripts/meson-buildoptions.sh

@@ -154,6 +154,7 @@ meson_options_help() {
   printf "%s\n" '  membarrier      membarrier system call (for Linux 4.14+ or Windows'
   printf "%s\n" '  modules         modules support (non Windows)'
   printf "%s\n" '  mpath           Multipath persistent reservation passthrough'
+  printf "%s\n" '  mshv            MSHV acceleration support'
   printf "%s\n" '  multiprocess    Out of process device emulation support'
   printf "%s\n" '  netmap          netmap network backend support'
   printf "%s\n" '  nettle          nettle cryptography support'
@@ -408,6 +409,8 @@ _meson_option_parse() {
     --disable-modules) printf "%s" -Dmodules=disabled ;;
     --enable-mpath) printf "%s" -Dmpath=enabled ;;
     --disable-mpath) printf "%s" -Dmpath=disabled ;;
+    --enable-mshv) printf "%s" -Dmshv=enabled ;;
+    --disable-mshv) printf "%s" -Dmshv=disabled ;;
     --enable-multiprocess) printf "%s" -Dmultiprocess=enabled ;;
     --disable-multiprocess) printf "%s" -Dmultiprocess=disabled ;;
     --enable-netmap) printf "%s" -Dnetmap=enabled ;;