i386: reorder call to cpu_exec_realizefn

i386 realizefn code is sensitive to ordering, and recent commits
aimed at refactoring it, splitting accelerator-specific code,
broke assumptions which need to be fixed.

We need to:

* process hyper-v enlightements first, as they assume features
  not to be expanded

* only then, expand features

* after expanding features, attempt to check them and modify them in the
  accel-specific realizefn code called by cpu_exec_realizefn().

* after the framework has been called via cpu_exec_realizefn,
  the code can check for what has or hasn't been set by accel-specific
  code, or extend its results, ie:

  - check and evenually set code_urev default
  - modify cpu->mwait after potentially being set from host CPUID.
  - finally check for phys_bits assuming all user and accel-specific
    adjustments have already been taken into account.

Fixes: f5cc5a5c ("i386: split cpu accelerators from cpu.c"...)
Fixes: 30565f10 ("cpu: call AccelCPUClass::cpu_realizefn in"...)
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Message-Id: <20210603123001.17843-2-cfontana@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index 5235bce8dc..00369c2000 100644
--- a/target/i386/kvm/kvm-cpu.c
+++ b/target/i386/kvm/kvm-cpu.c
@@ -26,10 +26,18 @@ static bool kvm_cpu_realizefn(CPUState *cs, Error **errp)
     /*
      * The realize order is important, since x86_cpu_realize() checks if
      * nothing else has been set by the user (or by accelerators) in
-     * cpu->ucode_rev and cpu->phys_bits.
+     * cpu->ucode_rev and cpu->phys_bits, and updates the CPUID results in
+     * mwait.ecx.
+     * This accel realization code also assumes cpu features are already expanded.
      *
      * realize order:
-     * kvm_cpu -> host_cpu -> x86_cpu
+     *
+     * x86_cpu_realize():
+     *  -> x86_cpu_expand_features()
+     *  -> cpu_exec_realizefn():
+     *            -> accel_cpu_realizefn()
+     *               kvm_cpu_realizefn() -> host_cpu_realizefn()
+     *  -> check/update ucode_rev, phys_bits, mwait
      */
     if (cpu->max_features) {
         if (enable_cpu_pm && kvm_has_waitpkg()) {