From: Marc Zyngier <maz@kernel.org>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: kvm@vger.kernel.org, Suzuki K Poulose <suzuki.poulose@arm.com>,
Jing Zhang <jingzhangos@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Sebastian Ott <sebott@redhat.com>,
Shusen Li <lishusen2@huawei.com>,
Waiman Long <longman@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-arm-kernel@lists.infradead.org,
Bjorn Helgaas <bhelgaas@google.com>,
Borislav Petkov <bp@alien8.de>, Anup Patel <anup@brainfault.org>,
Will Deacon <will@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Alexander Potapenko <glider@google.com>,
kvmarm@lists.linux.dev,
Keisuke Nishimura <keisuke.nishimura@inria.fr>,
Zenghui Yu <yuzenghui@huawei.com>,
Peter Zijlstra <peterz@infradead.org>,
Atish Patra <atishp@atishpatra.org>,
Joey Gouly <joey.gouly@arm.com>,
x86@kernel.org, Sean Christopherson <seanjc@google.com>,
Andre Przywara <andre.przywara@arm.com>,
Kunkun Jiang <jiangkunkun@huawei.com>,
linux-riscv@lists.infradead.org,
Randy Dunlap <rdunlap@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Alexandre Ghiti <alex@ghiti.fr>,
linux-kernel@vger.kernel.org,
Dave Hansen <dave.hansen@linux.intel.com>,
Oliver Upton <oliver.upton@linux.dev>,
kvm-riscv@lists.infradead.org, Ingo Molnar <mingo@redhat.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>
Subject: Re: [PATCH v5 3/6] KVM: add kvm_lock_all_vcpus and kvm_trylock_all_vcpus
Date: Wed, 14 May 2025 10:33:50 +0100 [thread overview]
Message-ID: <86o6vvfse9.wl-maz@kernel.org> (raw)
In-Reply-To: <20250512180407.659015-4-mlevitsk@redhat.com>
On Mon, 12 May 2025 19:04:04 +0100,
Maxim Levitsky <mlevitsk@redhat.com> wrote:
>
> In a few cases, usually in the initialization code, KVM locks all vCPUs
> of a VM to ensure that userspace doesn't do funny things while KVM performs
> an operation that affects the whole VM.
>
> Until now, all these operations were implemented using custom code,
> and all of them share the same problem:
>
> Lockdep can't cope with simultaneous locking of a large number of locks of
> the same class.
>
> However if these locks are taken while another lock is already held,
> which is luckily the case, it is possible to take advantage of little known
> _nest_lock feature of lockdep which allows in this case to have an
> unlimited number of locks of same class to be taken.
>
> To implement this, create two functions:
> kvm_lock_all_vcpus() and kvm_trylock_all_vcpus()
>
> Both functions are needed because some code that will be replaced in
> the subsequent patches, uses mutex_trylock, instead of regular mutex_lock.
>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Acked-by: Marc Zyngier <maz@kernel.org>
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2025-05-14 9:33 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-12 18:04 [PATCH v5 0/6] KVM: lockdep improvements Maxim Levitsky
2025-05-12 18:04 ` [PATCH v5 1/6] locking/mutex: implement mutex_trylock_nested Maxim Levitsky
2025-05-12 18:04 ` [PATCH v5 2/6] locking/mutex: implement mutex_lock_killable_nest_lock Maxim Levitsky
2025-05-12 18:04 ` [PATCH v5 3/6] KVM: add kvm_lock_all_vcpus and kvm_trylock_all_vcpus Maxim Levitsky
2025-05-14 9:33 ` Marc Zyngier [this message]
2025-05-12 18:04 ` [PATCH v5 4/6] x86: KVM: SVM: use kvm_lock_all_vcpus instead of a custom implementation Maxim Levitsky
2025-05-12 18:04 ` [PATCH v5 5/6] KVM: arm64: use kvm_trylock_all_vcpus when locking all vCPUs Maxim Levitsky
2025-05-14 9:35 ` Marc Zyngier
2025-05-12 18:04 ` [PATCH v5 6/6] RISC-V: KVM: " Maxim Levitsky
2025-05-13 11:18 ` Anup Patel
2025-05-13 11:45 ` [PATCH v5 0/6] KVM: lockdep improvements Peter Zijlstra
2025-05-27 16:23 ` Paolo Bonzini
2025-06-10 16:28 ` patchwork-bot+linux-riscv
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