linux-kernel - Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual suspend time injection

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Date:   Tue, 10 Aug 2021 17:24:52 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Hikaru Nishida <hikalium@...omium.org>,
        linux-kernel@...r.kernel.org, dme@....org, mlevitsk@...hat.com
Cc:     suleiman@...gle.com, Hikaru Nishida <hikalium@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        John Stultz <john.stultz@...aro.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        x86@...nel.org
Subject: Re: [v2 PATCH 3/4] x86/kvm: Add host side support for virtual
 suspend time injection

On Fri, Aug 06 2021 at 19:07, Hikaru Nishida wrote:
>  
> +#ifdef CONFIG_KVM_VIRT_SUSPEND_TIMING
> +void kvm_arch_timekeeping_inject_sleeptime(const struct timespec64 *delta)
> +{
> +	struct kvm_vcpu *vcpu;
> +	u64 suspend_time_ns;
> +	struct kvm *kvm;
> +	s64 adj;
> +	int i;
> +
> +	suspend_time_ns = timespec64_to_ns(delta);
> +	adj = tsc_khz * (suspend_time_ns / 1000000);
> +	/*
> +	 * Adjust TSCs on all vcpus and kvmclock as if they are stopped
> +	 * during host's suspension.
> +	 * Also, cummulative suspend time is recorded in kvm structure and
> +	 * the update will be notified via an interrupt for each vcpu.
> +	 */
> +	mutex_lock(&kvm_lock);

This is invoked from with timekeeper_lock held with interrupts
disabled. How is a mutex_lock() supposed to work here?

Thanks,

        tglx