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

Jan Kiszka
2010-02-24T23:46:01Z

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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 <jan.kiszka@siemens.com>
>> ---
>> 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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