linux-kernel - Re: [PATCH v4 5/5] x86: KVM: SEV: implement kvm_lock_all

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aBUxqZ6qgfYZLsye@google.com>
Date: Fri, 2 May 2025 13:57:13 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Maxim Levitsky <mlevitsk@...hat.com>
Cc: kvm@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	Kunkun Jiang <jiangkunkun@...wei.com>, Waiman Long <longman@...hat.com>, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	Catalin Marinas <catalin.marinas@....com>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Boqun Feng <boqun.feng@...il.com>, Borislav Petkov <bp@...en8.de>, Albert Ou <aou@...s.berkeley.edu>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Palmer Dabbelt <palmer@...belt.com>, 
	Alexandre Ghiti <alex@...ti.fr>, Alexander Potapenko <glider@...gle.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Andre Przywara <andre.przywara@....com>, x86@...nel.org, Joey Gouly <joey.gouly@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, kvm-riscv@...ts.infradead.org, 
	Atish Patra <atishp@...shpatra.org>, Ingo Molnar <mingo@...hat.com>, 
	Jing Zhang <jingzhangos@...gle.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, kvmarm@...ts.linux.dev, 
	Will Deacon <will@...nel.org>, Keisuke Nishimura <keisuke.nishimura@...ia.fr>, 
	Sebastian Ott <sebott@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Shusen Li <lishusen2@...wei.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Randy Dunlap <rdunlap@...radead.org>, Marc Zyngier <maz@...nel.org>, 
	Zenghui Yu <yuzenghui@...wei.com>
Subject: Re: [PATCH v4 5/5] x86: KVM: SEV: implement kvm_lock_all_vcpus and
 use it

On Wed, Apr 30, 2025, Maxim Levitsky wrote:
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 834f08dfa24c..9211b07b0565 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1392,6 +1392,31 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
>  }
>  EXPORT_SYMBOL_GPL(kvm_trylock_all_vcpus);
>  
> +/*
> + * Lock all of the VM's vCPUs.
> + * Assumes that the kvm->lock is held.

Add a lockdep assertion instead of a comment.

> + * Returns -EINTR if the process is killed.
> + */
> +int kvm_lock_all_vcpus(struct kvm *kvm)
> +{
> +	struct kvm_vcpu *vcpu;
> +	unsigned long i, j;
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm)

Needs curly braces.

> +		if (mutex_lock_killable_nest_lock(&vcpu->mutex, &kvm->lock))

I'd rather return mutex_lock_killable_nest_lock()'s error code verbatim.  Then
the function comment can go away, because the only thing remaining would be:

	/*
	 * Lock all of the VM's vCPUs.
	 /*

and that should be completely self-explanatory.  E.g.

int kvm_lock_all_vcpus(struct kvm *kvm)
{
	struct kvm_vcpu *vcpu;
	unsigned long i, j;
	int r;

	lockdep_assert_held(&kvm->lock);

	kvm_for_each_vcpu(i, vcpu, kvm) {
		r = mutex_lock_killable_nest_lock(&vcpu->mutex, &kvm->lock);
		if (r)
			goto out_unlock;
	}
	return 0;

out_unlock:
	kvm_for_each_vcpu(j, vcpu, kvm) {
		if (i == j)
			break;
		mutex_unlock(&vcpu->mutex);
	}
	return r;
}
EXPORT_SYMBOL_GPL(kvm_lock_all_vcpus);