Re: [Qemu-devel] [qom/qom-cpu PATCH] i386: invtsc migration blocker is redudant

[Juan Quintela]

Eduardo Habkost <address@hidden> wrote:
> On Tue, May 27, 2014 at 11:39:20AM -0300, Marcelo Tosatti wrote:
>> 
>> Migration blocker is redudant: blocking savevm is sufficient.
>> 
>
> Removing the redundancy looks welcome, but at the same time the
> migrate_add_blocker() call ensured we had a clearer error message (I
> mean: if we did mention invtsc in the error message, which we still
> don't, but should).
>
> I am not familiar with how we deal with savevm/migration errors, so I
> don't know what's best here. Juan, do you have any suggestions?


CHange unmigratable to Error * and add the message there?  First one
wins (or a way to combine them?).

Really I don't have a better idea.

Later, Juan.

>
> Additional small comment below:
>
>> Signed-off-by: Marcelo Tosatti <address@hidden>
>> 
>> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
>> index f9ffa4b..b29098a 100644
>> --- a/target-i386/kvm.c
>> +++ b/target-i386/kvm.c
>> @@ -450,7 +450,7 @@ static bool hyperv_enabled(X86CPU *cpu)
>>              cpu->hyperv_relaxed_timing);
>>  }
>>  
>> -static Error *invtsc_mig_blocker;
>> +bool invtsc_mig_blocked;
>>  
>>  #define KVM_MAX_CPUID_ENTRIES  100
>>  
>> @@ -708,13 +708,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
>>      }
>>  
>>      c = cpuid_find_entry(&cpuid_data.cpuid, 0x80000007, 0);
>> -    if (c && (c->edx & 1<<8) && invtsc_mig_blocker == NULL) {
>> -        /* for migration */
>> -        error_setg(&invtsc_mig_blocker,
>> -                   "State blocked by non-migratable CPU device");
>> -        migrate_add_blocker(invtsc_mig_blocker);
>> -        /* for savevm */
>> +    if (c && (c->edx & 1<<8) && invtsc_mig_blocked == false) {
>>          vmstate_x86_cpu.unmigratable = 1;
>> +        invtsc_mig_blocked = true;
>
> Why the invtsc_mig_blocked variable? Setting unmigratable=1 twice won't
> hurt anybody.
>
>>      }
>>