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 10:48:26 +0200 [thread overview]
Message-ID: <0cfb1f41-381f-6621-0fe7-14a54059a90d@redhat.com> (raw)
In-Reply-To: <20220429010312.4013-1-hdanton@sina.com>
On 4/29/22 03:03, Hillf Danton wrote:
> Wonder if local lock classes [1] help.
>
> [1]https://lore.kernel.org/lkml/165055518776.3745911.9346998911322224736.stgit@dwillia2-desk3.amr.corp.intel.com/
No, they wouldn't. Local lock classes are more of a per-subsystem lock,
while here the issue is that we are taking an arbitrary amount of locks
at the same time.
Technically it would be possible to put a struct lock_class_key in
struct kvm_vcpu, but that wouldn't scale and would actually _reduce_ the
likelihood of lockdep reporting bad things.
The effectiveness of lockdep comes exactly from using the same map for
all locks in the class, so that AB/BA scenarios are caught throughout
the whole life of the system. If each lock has a separate they would be
caught only if the "B" is exactly the same mutex in both AB and BA cases.
Paolo
next prev parent reply other threads:[~2022-04-29 8:48 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 [this message]
[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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