Re: [PATCH v4 3/9] target/i386/kvm: Only save/load kvmclock MSRs when kvmclock enabled

["Chen, Zide" <zide.chen@intel.com>]

On 7/16/2024 9:10 AM, Zhao Liu wrote:
> MSR_KVM_SYSTEM_TIME and MSR_KVM_WALL_CLOCK are attached with the (old)
> kvmclock feature (KVM_FEATURE_CLOCKSOURCE).
> 
> So, just save/load them only when kvmclock (KVM_FEATURE_CLOCKSOURCE) is
> enabled.
> 
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>

 Reviewed-by: Zide Chen <zide.chen@intel.com>


> ---
>  target/i386/kvm/kvm.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index 6ad5a7dbf1fd..ac434e83b64c 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -3419,8 +3419,10 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
>       */
>      if (level >= KVM_PUT_RESET_STATE) {
>          kvm_msr_entry_add(cpu, MSR_IA32_TSC, env->tsc);
> -        kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
> -        kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
> +        if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK) {
> +            kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr);
> +            kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
> +        }
>          if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
>              kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, env->async_pf_int_msr);
>          }
> @@ -3895,8 +3897,10 @@ static int kvm_get_msrs(X86CPU *cpu)
>          }
>      }
>  #endif
> -    kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
> -    kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
> +    if (env->features[FEAT_KVM] & CPUID_KVM_CLOCK) {
> +        kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, 0);
> +        kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, 0);
> +    }
>      if (env->features[FEAT_KVM] & CPUID_KVM_ASYNCPF_INT) {
>          kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_INT, 0);
>      }