On Thu, Apr 24, 2014 at 06:32:42PM -0300, Marcelo Tosatti wrote:
> On Thu, Apr 24, 2014 at 04:21:59PM -0300, Eduardo Habkost wrote:
> > On Wed, Apr 23, 2014 at 06:04:45PM -0300, Marcelo Tosatti wrote:
> > >
> > > Invariant TSC documentation mentions that "invariant TSC will run at a
> > > constant rate in all ACPI P-, C-. and T-states".
> > >
> > > This is not the case if migration to a host with different TSC frequency
> > > is allowed, or if savevm is performed. So block migration/savevm.
> > >
> > > Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
> > >
> > [...]
> > > @@ -702,6 +706,16 @@ int kvm_arch_init_vcpu(CPUState *cs)
> > > !!(c->ecx & CPUID_EXT_SMX);
> > > }
> > >
> > > + c = cpuid_find_entry(&cpuid_data.cpuid, 0x80000007, 0);
> > > + if (c && (c->edx & 1<<8) && invtsc_mig_blocker == NULL) {
> > > + /* for migration */
> > > + error_set(&invtsc_mig_blocker,
> > > + QERR_DEVICE_FEATURE_BLOCKS_MIGRATION, "invtsc", "cpu");
> > > + migrate_add_blocker(invtsc_mig_blocker);
> > > + /* for savevm */
> > > + vmstate_x86_cpu.unmigratable = 1;
> >
> > Did you ensure this will always happen before vmstate_register() is
> > called for vmstate_x86_cpu? I believe kvm_arch_init_vcpu() is called a
> > long long time after device_set_realized() (which is where
> > vmstate_register() is called for DeviceState objects).
>
> x86_cpu_realizefn
x86_cpu_realizefn is called by device_set_realized (via
DeviceClass.realize), but vmstate_register*() is called _after_
DeviceClass.realize.
Continuing:
> -> qemu_init_vcpu -> qemu_kvm_start_vcpu ->
> qemu_kvm_cpu_thread_fn
^^^^ this is run in a new thread
> -> kvm_init_vcpu -> kvm_arch_init_vcpu
^^^^ this is called after acquiring qemu_global_mutex.
Then it gets tricky: qemu_kvm_start_vcpu() returns only after
cpu->created is set, which is done after kvm_arch_init_vcpu() is called.
BUT:
I was mistaken. This is not where vmstate_x86_cpu is registered. It is at
cpu_exec_init(). And cpu_exec_init() is called much earlier, at
x86_cpu_initfn(). See the printf() results below.
Have you tested if your patch actually blocks savevm?
>
>
> @@ -2573,6 +2598,8 @@ static void x86_cpu_realizefn(DeviceState *dev,
> Error **errp)
> CPUX86State *env = &cpu->env;
> Error *local_err = NULL;
>
> + printf("%s: dev->realized=%d\n", __func__, dev->realized);
> +
> if (env->features[FEAT_7_0_EBX] && env->cpuid_level < 7) {
> env->cpuid_level = 7;
> }
>
>
>
> QEMU 1.7.93 monitor - type 'help' for more information
> (qemu) x86_cpu_realizefn: dev->realized=0
> x86_cpu_realizefn: dev->realized=0
> audio: Could not init `oss' audio driver
diff --git a/exec.c b/exec.c
index 91513c6..1fd3e12 100644
--- a/exec.c
+++ b/exec.c
@@ -505,6 +505,7 @@ void cpu_exec_init(CPUArchState *env)
assert(qdev_get_vmsd(DEVICE(cpu)) == NULL);
#endif
if (cc->vmsd != NULL) {
+ printf("registering CPUClass.vmsd\n");
vmstate_register(NULL, cpu_index, cc->vmsd, cpu);
}
}
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 73643d7..42c874c 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -468,6 +468,7 @@ int kvm_arch_init_vcpu(CPUState *cs)
int kvm_base = KVM_CPUID_SIGNATURE;
int r;
+ printf("%s: realized=%d\n", __func__, DEVICE(cpu)->realized);
memset(&cpuid_data, 0, sizeof(cpuid_data));
cpuid_i = 0;
QEMU 2.0.50 monitor - type 'help' for more information
(qemu) registering CPUClass.vmsd
kvm_arch_init_vcpu: realized=0
--
Eduardo
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