linux-kernel - Re: [PATCH] KVM: SEV: Add lock subtyping in sev_lock_two_vms so lockdep doesn't report false dependencies

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Date:   Fri, 7 Jan 2022 18:01:14 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: SEV: Add lock subtyping in sev_lock_two_vms so
 lockdep doesn't report false dependencies

On 1/5/22 07:41, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> Both source and dest vms' kvm->locks are held in sev_lock_two_vms,
> we should mark one with different subtype to avoid false positives
> from lockdep.
> 
> Fixes: c9d61dcb0bc26 (KVM: SEV: accept signals in sev_lock_two_vms)
> Reported-by: Yiru Xu <xyru1999@...il.com>
> Tested-by: Jinrong Liang <cloudliang@...cent.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>   arch/x86/kvm/svm/sev.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 7656a2c..be28831 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1565,7 +1565,7 @@ static int sev_lock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
>   	r = -EINTR;
>   	if (mutex_lock_killable(&dst_kvm->lock))
>   		goto release_src;
> -	if (mutex_lock_killable(&src_kvm->lock))
> +	if (mutex_lock_killable_nested(&src_kvm->lock, SINGLE_DEPTH_NESTING))
>   		goto unlock_dst;
>   	return 0;
>   

Queued, thanks.

Paolo