[Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback

[Jan Kiszka]

Marcelo Tosatti wrote:
> On Wed, Feb 24, 2010 at 03:17:55PM +0100, Jan Kiszka wrote:
>> Drop kvm_load_tsc in favor of level-dependent writeback in
>> kvm_arch_load_regs. KVM's PV clock MSRs fall in the same category and
>> should therefore only be written back on full sync.
>>
>> Signed-off-by: Jan Kiszka <address@hidden>
>> ---
>>  qemu-kvm-x86.c        |   19 +++++--------------
>>  qemu-kvm.h            |    4 ----
>>  target-i386/machine.c |    5 -----
>>  3 files changed, 5 insertions(+), 23 deletions(-)
>>
>> diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
>> index 840c1c9..84fd7fa 100644
>> --- a/qemu-kvm-x86.c
>> +++ b/qemu-kvm-x86.c
>> @@ -965,8 +965,11 @@ void kvm_arch_load_regs(CPUState *env, int level)
>>          set_msr_entry(&msrs[n++], MSR_LSTAR  ,           env->lstar);
>>      }
>>  #endif
>> -    set_msr_entry(&msrs[n++], MSR_KVM_SYSTEM_TIME,  env->system_time_msr);
>> -    set_msr_entry(&msrs[n++], MSR_KVM_WALL_CLOCK,  env->wall_clock_msr);
>> +    if (level == KVM_PUT_FULL_STATE) {
>> +        set_msr_entry(&msrs[n++], MSR_IA32_TSC, env->tsc);
>> +        set_msr_entry(&msrs[n++], MSR_KVM_SYSTEM_TIME, 
>> env->system_time_msr);
>> +        set_msr_entry(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
>> +    }
> 
> As things stand today, the TSC should only be written on migration. See
> 53f658b3c33616a4997ee254311b335e59063289 in the kernel.

Migration and power-up - that's what this patch ensures (=>
KVM_PUT_FULL_STATE). Or where do you see any problem?

Jan

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