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From: Paolo Bonzini <pbonzini@redhat.com>
To: Hillf Danton <hdanton@sina.com>
Cc: Peter Gonda <pgonda@google.com>,
	Sean Christopherson <seanjc@google.com>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3] KVM: SEV: Mark nested locking of vcpu->lock
Date: Fri, 29 Apr 2022 15:44:42 +0200	[thread overview]
Message-ID: <b63a373a-be17-33ca-11f6-2dd36162844b@redhat.com> (raw)
In-Reply-To: <20220429114012.4127-1-hdanton@sina.com>

On 4/29/22 13:40, Hillf Danton wrote:
> To avoid acquiring more than one mutexes at the same time, add a completion
> in paralle to the mutex in question and ask mutex locker for non-migration
> purpose to take a nap on completion instead of mutex.

Acquiring more than one mutex at a time is perfectly fine.  It also 
cannot get into philosophers-problem-like deadlocks because 1) it's got 
a well-defined iteration order 2) it's protected by sev_lock_two_vms.

Just, lockdep that has to be convinced that it is fine.  I don't shy 
away from complex locking schemes if they're necessary, but here it 
absolutely isn't.

Paolo


  parent reply	other threads:[~2022-04-29 13:44 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-07 19:59 [PATCH v3] KVM: SEV: Mark nested locking of vcpu->lock Peter Gonda
2022-04-07 21:17 ` John Sperbeck
2022-04-08 15:08   ` Peter Gonda
2022-04-20 20:14     ` Peter Gonda
2022-04-21 15:56       ` Paolo Bonzini
2022-04-26 19:06         ` Peter Gonda
2022-04-27 16:04           ` Paolo Bonzini
2022-04-27 20:18             ` Peter Gonda
2022-04-28 21:28               ` Peter Gonda
2022-04-28 23:59                 ` Paolo Bonzini
2022-04-29 15:35                   ` Peter Gonda
2022-04-29 15:38                     ` Paolo Bonzini
2022-04-29 15:51                       ` Peter Gonda
2022-04-29 15:58                         ` Paolo Bonzini
2022-04-29 17:12                           ` Peter Gonda
2022-04-29 17:21                             ` Paolo Bonzini
2022-04-29 17:27                               ` Peter Gonda
2022-04-29 17:32                                 ` Paolo Bonzini
2022-04-29 17:33                                   ` Peter Gonda
     [not found]                 ` <20220429010312.4013-1-hdanton@sina.com>
2022-04-29  8:48                   ` Paolo Bonzini
     [not found]                   ` <20220429114012.4127-1-hdanton@sina.com>
2022-04-29 13:44                     ` Paolo Bonzini [this message]
     [not found]                     ` <20220430015008.4257-1-hdanton@sina.com>
2022-04-30  8:11                       ` Paolo Bonzini
2022-04-30  8:11                       ` Paolo Bonzini

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