From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC8632135AD for ; Wed, 9 Apr 2025 20:45:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744231538; cv=none; b=KKeDmnXTgS3AprN8256r9cDfGGnsTbW8YHY0Bc8oRSIqgojv8ZZIeKyNVy4LSKYS0vPk9IBRaLoCKaN/gZEGg7MM7MtlEcIvdPjXugdOAicFFj0HrSMs48Th1bq5swBFsWf5Kw1MkXVdkgikaq36AJm/llIk1Ns4ULNL2lNdpsA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744231538; c=relaxed/simple; bh=xOp9DXsMQrw85PtagiwlHyz33EONNax0oXOrZSgcHHk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cuV1gGQcIhEgiWP5JnY1bEZDiE76pkxpzcV7XmZt3CSbs7OLPu+8WIdfJi/sNcrMjzvFRrdFYcBC7fYMhuiIgLfUeicZjX282/TRokqlUVcEA+Et5idBhf1PQOdtjK2GB3JS5gV1/YibSBij28Yk8PQGSQ/Ab9W8CBZOTtzg/Xk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=xC8aSKQf; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="xC8aSKQf" Date: Wed, 9 Apr 2025 13:45:12 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1744231523; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ENOcZPIItp2JvszVxj/GE2Qd8ZKfpfM4JflKxCvjNwk=; b=xC8aSKQfjMqodNcjkUTLUjs/zqCFYnuOpjbh5P9WpT5NQV26kzbmBYXpCKWYi7kZGBKsxL gZW41lEMVPwc0O3ZChQyXo3FcMfH90y50iz05hYThAcZmGJ8iVYi08BYw8+X5iWzs50Hx2 w3VkprowZiWZQ4RRthwlJQvvZgV2B04= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Maxim Levitsky Cc: kvm@vger.kernel.org, Alexander Potapenko , "H. Peter Anvin" , Suzuki K Poulose , kvm-riscv@lists.infradead.org, Dave Hansen , Jing Zhang , Waiman Long , x86@kernel.org, Kunkun Jiang , Boqun Feng , Anup Patel , Albert Ou , kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Zenghui Yu , Borislav Petkov , Alexandre Ghiti , Keisuke Nishimura , Sebastian Ott , Paolo Bonzini , Atish Patra , Paul Walmsley , Randy Dunlap , Will Deacon , Palmer Dabbelt , linux-riscv@lists.infradead.org, Marc Zyngier , linux-arm-kernel@lists.infradead.org, Joey Gouly , Peter Zijlstra , Ingo Molnar , Andre Przywara , Thomas Gleixner , Sean Christopherson , Catalin Marinas , Bjorn Helgaas Subject: Re: [PATCH v2 2/4] KVM: x86: move sev_lock/unlock_vcpus_for_migration to kvm_main.c Message-ID: References: <20250409014136.2816971-1-mlevitsk@redhat.com> <20250409014136.2816971-3-mlevitsk@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250409014136.2816971-3-mlevitsk@redhat.com> X-Migadu-Flow: FLOW_OUT On Tue, Apr 08, 2025 at 09:41:34PM -0400, Maxim Levitsky wrote: > Move sev_lock/unlock_vcpus_for_migration to kvm_main and call the > new functions the kvm_lock_all_vcpus/kvm_unlock_all_vcpus > and kvm_lock_all_vcpus_nested. > > This code allows to lock all vCPUs without triggering lockdep warning > about reaching MAX_LOCK_DEPTH depth by coercing the lockdep into > thinking that we release all the locks other than vcpu'0 lock > immediately after we take them. > > No functional change intended. > > Suggested-by: Paolo Bonzini > Signed-off-by: Maxim Levitsky > --- > arch/x86/kvm/svm/sev.c | 65 +++--------------------------------- > include/linux/kvm_host.h | 6 ++++ > virt/kvm/kvm_main.c | 71 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 81 insertions(+), 61 deletions(-) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 0bc708ee2788..7adc54b1f741 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -1889,63 +1889,6 @@ enum sev_migration_role { > SEV_NR_MIGRATION_ROLES, > }; > > -static int sev_lock_vcpus_for_migration(struct kvm *kvm, > - enum sev_migration_role role) > -{ > - struct kvm_vcpu *vcpu; > - unsigned long i, j; > - > - kvm_for_each_vcpu(i, vcpu, kvm) { > - if (mutex_lock_killable_nested(&vcpu->mutex, role)) > - goto out_unlock; > - > -#ifdef CONFIG_PROVE_LOCKING > - if (!i) > - /* > - * Reset the role to one that avoids colliding with > - * the role used for the first vcpu mutex. > - */ > - role = SEV_NR_MIGRATION_ROLES; > - else > - mutex_release(&vcpu->mutex.dep_map, _THIS_IP_); > -#endif > - } > - > - return 0; > - > -out_unlock: > - > - kvm_for_each_vcpu(j, vcpu, kvm) { > - if (i == j) > - break; > - > -#ifdef CONFIG_PROVE_LOCKING > - if (j) > - mutex_acquire(&vcpu->mutex.dep_map, role, 0, _THIS_IP_); > -#endif > - > - mutex_unlock(&vcpu->mutex); > - } > - return -EINTR; > -} > - > -static void sev_unlock_vcpus_for_migration(struct kvm *kvm) > -{ > - struct kvm_vcpu *vcpu; > - unsigned long i; > - bool first = true; > - > - kvm_for_each_vcpu(i, vcpu, kvm) { > - if (first) > - first = false; > - else > - mutex_acquire(&vcpu->mutex.dep_map, > - SEV_NR_MIGRATION_ROLES, 0, _THIS_IP_); > - > - mutex_unlock(&vcpu->mutex); > - } > -} > - > static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm) > { > struct kvm_sev_info *dst = to_kvm_sev_info(dst_kvm); > @@ -2083,10 +2026,10 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd) > charged = true; > } > > - ret = sev_lock_vcpus_for_migration(kvm, SEV_MIGRATION_SOURCE); > + ret = kvm_lock_all_vcpus_nested(kvm, false, SEV_MIGRATION_SOURCE); > if (ret) > goto out_dst_cgroup; > - ret = sev_lock_vcpus_for_migration(source_kvm, SEV_MIGRATION_TARGET); > + ret = kvm_lock_all_vcpus_nested(source_kvm, false, SEV_MIGRATION_TARGET); > if (ret) > goto out_dst_vcpu; > > @@ -2100,9 +2043,9 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd) > ret = 0; > > out_source_vcpu: > - sev_unlock_vcpus_for_migration(source_kvm); > + kvm_unlock_all_vcpus(source_kvm); > out_dst_vcpu: > - sev_unlock_vcpus_for_migration(kvm); > + kvm_unlock_all_vcpus(kvm); > out_dst_cgroup: > /* Operates on the source on success, on the destination on failure. */ > if (charged) > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 1dedc421b3e3..30cf28bf5c80 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1015,6 +1015,12 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id) > > void kvm_destroy_vcpus(struct kvm *kvm); > > +int kvm_lock_all_vcpus_nested(struct kvm *kvm, bool trylock, unsigned int role); > +void kvm_unlock_all_vcpus(struct kvm *kvm); > + > +#define kvm_lock_all_vcpus(kvm, trylock) \ > + kvm_lock_all_vcpus_nested(kvm, trylock, 0) > + Can you instead add lock / trylock variants of this? kvm_trylock_all_vcpus(kvm) seems a bit more obvious in the calling code. Thanks, Oliver