答复: [PATCH][v2] KVM: x86: directly call wbinvd for local cpu when emulate wbinvd

["Li,Rongqing" <lirongqing@baidu.com>]

Ping 

-Li

> -----邮件原件-----
> 发件人: Li,Rongqing <lirongqing@baidu.com>
> 发送时间: 2021年10月13日 17:43
> 收件人: x86@kernel.org; kvm@vger.kernel.org; Li,Rongqing
> <lirongqing@baidu.com>
> 主题: [PATCH][v2] KVM: x86: directly call wbinvd for local cpu when emulate
> wbinvd
> 
> directly call wbinvd for local cpu, instead of calling atomic cpumask_set_cpu to
> set local cpu, and then check if local cpu needs to run in on_each_cpu_mask
> 
> on_each_cpu_mask is less efficient than smp_call_function_many, since it will
> close preempt again and running call function by checking flag with
> SCF_RUN_LOCAL. and here wbinvd can be called directly
> 
> In fact, This change reverts commit 2eec73437487 ("KVM: x86: Avoid issuing
> wbinvd twice"), since smp_call_function_many is skiping the local cpu (as
> description of c2162e13d6e2f), wbinvd is not issued twice
> 
> and reverts commit c2162e13d6e2f ("KVM: X86: Fix missing local pCPU when
> executing wbinvd on all dirty pCPUs") too, which fixed the previous patch, when
> revert previous patch, it is not needed.
> 
> Signed-off-by: Li RongQing <lirongqing@baidu.com>
> ---
> diff v2: rewrite commit log
> 
>  arch/x86/kvm/x86.c |   13 ++++++-------
>  1 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index aabd3a2..28c4c72
> 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6991,15 +6991,14 @@ static int kvm_emulate_wbinvd_noskip(struct
> kvm_vcpu *vcpu)
>  		return X86EMUL_CONTINUE;
> 
>  	if (static_call(kvm_x86_has_wbinvd_exit)()) {
> -		int cpu = get_cpu();
> -
> -		cpumask_set_cpu(cpu, vcpu->arch.wbinvd_dirty_mask);
> -		on_each_cpu_mask(vcpu->arch.wbinvd_dirty_mask,
> +		preempt_disable();
> +		smp_call_function_many(vcpu->arch.wbinvd_dirty_mask,
>  				wbinvd_ipi, NULL, 1);
> -		put_cpu();
> +		preempt_enable();
>  		cpumask_clear(vcpu->arch.wbinvd_dirty_mask);
> -	} else
> -		wbinvd();
> +	}
> +
> +	wbinvd();
>  	return X86EMUL_CONTINUE;
>  }
> 
> --
> 1.7.1