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@xxxxxxxxxx>
Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Claudio Fontana <cfontana@xxxxxxx>
---
target/i386/cpu.c | 79 +++++++++++++++++++++++++--------------
target/i386/kvm/kvm-cpu.c | 12 +++++-
2 files changed, 61 insertions(+), 30 deletions(-)
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 9e211ac2ce..f7eb5f7f6e 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -6133,39 +6133,17 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
Error *local_err = NULL;
static bool ht_warned;
- /* Process Hyper-V enlightenments */
- x86_cpu_hyperv_realize(cpu);
-
- cpu_exec_realizefn(cs, &local_err);
- if (local_err != NULL) {
- error_propagate(errp, local_err);
- return;
- }
-
- if (xcc->host_cpuid_required && !accel_uses_host_cpuid()) {
- g_autofree char *name = x86_cpu_class_get_model_name(xcc);
- error_setg(&local_err, "CPU model '%s' requires KVM or HVF", name);
- goto out;
- }
-
- if (cpu->ucode_rev == 0) {
- /* The default is the same as KVM's. */
- if (IS_AMD_CPU(env)) {
- cpu->ucode_rev = 0x01000065;
- } else {
- cpu->ucode_rev = 0x100000000ULL;
- }
- }
-
- /* mwait extended info: needed for Core compatibility */
- /* We always wake on interrupt even if host does not have the capability */
- cpu->mwait.ecx |= CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;
-
if (cpu->apic_id == UNASSIGNED_APIC_ID) {
error_setg(errp, "apic-id property was not initialized properly");
return;
}
+ /*
+ * Process Hyper-V enlightenments.
+ * Note: this currently has to happen before the expansion of CPU features.
+ */
+ x86_cpu_hyperv_realize(cpu);
+
x86_cpu_expand_features(cpu, &local_err);
if (local_err) {
goto out;
@@ -6190,11 +6168,56 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
& CPUID_EXT2_AMD_ALIASES);
}
+ /*
+ * note: the call to the framework needs to happen after feature expansion,
+ * but before the checks/modifications to ucode_rev, mwait, phys_bits.
+ * These may be set by the accel-specific code,
+ * and the results are subsequently checked / assumed in this function.
+ */
+ cpu_exec_realizefn(cs, &local_err);
+ if (local_err != NULL) {
+ error_propagate(errp, local_err);
+ return;
+ }
+
+ if (xcc->host_cpuid_required && !accel_uses_host_cpuid()) {
+ g_autofree char *name = x86_cpu_class_get_model_name(xcc);
+ error_setg(&local_err, "CPU model '%s' requires KVM or HVF", name);
+ goto out;
+ }
+
+ if (cpu->ucode_rev == 0) {
+ /*
+ * The default is the same as KVM's. Note that this check
+ * needs to happen after the evenual setting of ucode_rev in
+ * accel-specific code in cpu_exec_realizefn.
+ */
+ if (IS_AMD_CPU(env)) {
+ cpu->ucode_rev = 0x01000065;
+ } else {
+ cpu->ucode_rev = 0x100000000ULL;
+ }
+ }
+
+ /*
+ * mwait extended info: needed for Core compatibility
+ * We always wake on interrupt even if host does not have the capability.
+ *
+ * requires the accel-specific code in cpu_exec_realizefn to
+ * have already acquired the CPUID data into cpu->mwait.
+ */
+ cpu->mwait.ecx |= CPUID_MWAIT_EMX | CPUID_MWAIT_IBE;
+
/* For 64bit systems think about the number of physical bits to present.
* ideally this should be the same as the host; anything other than matching
* the host can cause incorrect guest behaviour.
* QEMU used to pick the magic value of 40 bits that corresponds to
* consumer AMD devices but nothing else.
+ *
+ * Note that this code assumes features expansion has already been done
+ * (as it checks for CPUID_EXT2_LM), and also assumes that potential
+ * phys_bits adjustments to match the host have been already done in
+ * accel-specific code in cpu_exec_realizefn.
*/
if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
if (cpu->phys_bits &&
diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index c660ad4293..afd5f01413 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()) {
--
2.26.2
