linux-kernel - Re: [PATCH v4 10/26] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm

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Message-ID: <20220910181143.GC699006@ls.amr.corp.intel.com>
Date:   Sat, 10 Sep 2022 11:11:43 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     isaku.yamahata@...el.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Yuan Yao <yuan.yao@...ux.intel.com>, isaku.yamahata@...il.com,
        Kai Huang <kai.huang@...el.com>,
        Atish Patra <atishp@...shpatra.org>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>,
        Qi Liu <liuqi115@...wei.com>,
        John Garry <john.garry@...wei.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Huang Ying <ying.huang@...el.com>,
        Huacai Chen <chenhuacai@...nel.org>
Subject: Re: [PATCH v4 10/26] KVM: Drop kvm_count_lock and instead protect
 kvm_usage_count with kvm_lock

On Fri, Sep 09, 2022 at 11:05:34AM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> >+	 * cpu_hotplug_disable() and other CPUs are offlined.  No need for
> >+	 * locking.
> >+	 */
> >+	lockdep_assert_not_held(&kvm_lock);
> >+
> >+	if (kvm_usage_count) {
> >+		preempt_disable();
> > 		hardware_disable_nolock(NULL);
> >+		preempt_enable();
> 
> kvm_suspend() is called with interrupt disabled. So, no need to disable
> preemption.
> 
> /**
>  * syscore_suspend - Execute all the registered system core suspend callbacks.
>  *
>  * This function is executed with one CPU on-line and disabled interrupts.
>  */
> int syscore_suspend(void)

Thanks, I'll fix it with a comment.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>