From: Peter Gonda <pgonda@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: John Sperbeck <jsperbeck@google.com>,
kvm list <kvm@vger.kernel.org>,
David Rientjes <rientjes@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: Tue, 26 Apr 2022 13:06:57 -0600 [thread overview]
Message-ID: <CAMkAt6q6YLBfo2RceduSXTafckEehawhD4K4hUEuB4ZNqe2kKg@mail.gmail.com> (raw)
In-Reply-To: <62e9ece1-5d71-f803-3f65-2755160cf1d1@redhat.com>
On Thu, Apr 21, 2022 at 9:56 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 4/20/22 22:14, Peter Gonda wrote:
> >>>> svm_vm_migrate_from() uses sev_lock_vcpus_for_migration() to lock all
> >>>> source and target vcpu->locks. Mark the nested subclasses to avoid false
> >>>> positives from lockdep.
> >> Nope. Good catch, I didn't realize there was a limit 8 subclasses:
> > Does anyone have thoughts on how we can resolve this vCPU locking with
> > the 8 subclass max?
>
> The documentation does not have anything. Maybe you can call
> mutex_release manually (and mutex_acquire before unlocking).
>
> Paolo
Hmm this seems to be working thanks Paolo. To lock I have been using:
...
if (mutex_lock_killable_nested(
&vcpu->mutex, i * SEV_NR_MIGRATION_ROLES + role))
goto out_unlock;
mutex_release(&vcpu->mutex.dep_map, _THIS_IP_);
...
To unlock:
...
mutex_acquire(&vcpu->mutex.dep_map, 0, 0, _THIS_IP_);
mutex_unlock(&vcpu->mutex);
...
If I understand correctly we are fully disabling lockdep by doing
this. If this is the case should I just remove all the '_nested' usage
so switch to mutex_lock_killable() and remove the per vCPU subclass?
next prev parent reply other threads:[~2022-04-26 19:08 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 [this message]
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
[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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