From nobody Fri Dec 19 07:48:00 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 941E4C61D9D for ; Sat, 25 Nov 2023 08:34:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231819AbjKYIeK (ORCPT ); Sat, 25 Nov 2023 03:34:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231782AbjKYIeA (ORCPT ); Sat, 25 Nov 2023 03:34:00 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26EC010E4 for ; Sat, 25 Nov 2023 00:34:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1700901245; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gPrF/vSjRPm2fd0sspMYyxzeSYwBWlkCsnLNpcIl0aE=; b=Iep9fvAUio00rnvWjvlXChyYBZdVgu6GN8corDyFhsRuXV8zsudfJAg64UpFfhYyG9AD3o 0wXVJEZj9HNIGIp9upIMBh+k8kJRq15YA+nHDoWTNnKCfk4BxsSMy36CROk1Oz7839nnmP F0vVM9NI+fFbl+rLPqF3z/32aXonPAw= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-454-jgv7MS3gP9-R5CC6iMbj8w-1; Sat, 25 Nov 2023 03:34:01 -0500 X-MC-Unique: jgv7MS3gP9-R5CC6iMbj8w-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6D94D3C00096; Sat, 25 Nov 2023 08:34:01 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id EBFBE1121306; Sat, 25 Nov 2023 08:34:00 +0000 (UTC) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: seanjc@google.com, mlevitsk@redhat.com Subject: [PATCH v2 1/4] KVM: x86/mmu: remove unnecessary "bool shared" argument from functions Date: Sat, 25 Nov 2023 03:33:57 -0500 Message-Id: <20231125083400.1399197-2-pbonzini@redhat.com> In-Reply-To: <20231125083400.1399197-1-pbonzini@redhat.com> References: <20231125083400.1399197-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Neither tdp_mmu_next_root nor kvm_tdp_mmu_put_root need to know if the lock is taken for read or write. Either way, protection is achieved via RCU and tdp_mmu_pages_lock. Remove the argument and just assert that the lock is taken. Reviewed-by: Maxim Levitsky Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 2 +- arch/x86/kvm/mmu/tdp_mmu.c | 34 +++++++++++++++++++++------------- arch/x86/kvm/mmu/tdp_mmu.h | 3 +-- 3 files changed, 23 insertions(+), 16 deletions(-) v1->v2: comment tweak diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index c57e181bba21..1cb81573a60b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3556,7 +3556,7 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t= *root_hpa, return; =20 if (is_tdp_mmu_page(sp)) - kvm_tdp_mmu_put_root(kvm, sp, false); + kvm_tdp_mmu_put_root(kvm, sp); else if (!--sp->root_count && sp->role.invalid) kvm_mmu_prepare_zap_page(kvm, sp, invalid_list); =20 diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 6cd4dd631a2f..05689c8d45b7 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -73,10 +73,13 @@ static void tdp_mmu_free_sp_rcu_callback(struct rcu_hea= d *head) tdp_mmu_free_sp(sp); } =20 -void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root, - bool shared) +void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root) { - kvm_lockdep_assert_mmu_lock_held(kvm, shared); + /* + * Either read or write is okay, but mmu_lock must be held because + * writers are not required to take tdp_mmu_pages_lock. + */ + lockdep_assert_held(&kvm->mmu_lock); =20 if (!refcount_dec_and_test(&root->tdp_mmu_root_count)) return; @@ -106,10 +109,16 @@ void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm= _mmu_page *root, */ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm, struct kvm_mmu_page *prev_root, - bool shared, bool only_valid) + bool only_valid) { struct kvm_mmu_page *next_root; =20 + /* + * While the roots themselves are RCU-protected, fields such as + * role.invalid are protected by mmu_lock. + */ + lockdep_assert_held(&kvm->mmu_lock); + rcu_read_lock(); =20 if (prev_root) @@ -132,7 +141,7 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kv= m *kvm, rcu_read_unlock(); =20 if (prev_root) - kvm_tdp_mmu_put_root(kvm, prev_root, shared); + kvm_tdp_mmu_put_root(kvm, prev_root); =20 return next_root; } @@ -144,13 +153,12 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct = kvm *kvm, * recent root. (Unless keeping a live reference is desirable.) * * If shared is set, this function is operating under the MMU lock in read - * mode. In the unlikely event that this thread must free a root, the lock - * will be temporarily dropped and reacquired in write mode. + * mode. */ #define __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, _= only_valid)\ - for (_root =3D tdp_mmu_next_root(_kvm, NULL, _shared, _only_valid); \ + for (_root =3D tdp_mmu_next_root(_kvm, NULL, _only_valid); \ _root; \ - _root =3D tdp_mmu_next_root(_kvm, _root, _shared, _only_valid)) \ + _root =3D tdp_mmu_next_root(_kvm, _root, _only_valid)) \ if (kvm_lockdep_assert_mmu_lock_held(_kvm, _shared) && \ kvm_mmu_page_as_id(_root) !=3D _as_id) { \ } else @@ -159,9 +167,9 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kv= m *kvm, __for_each_tdp_mmu_root_yield_safe(_kvm, _root, _as_id, _shared, true) =20 #define for_each_tdp_mmu_root_yield_safe(_kvm, _root, _shared) \ - for (_root =3D tdp_mmu_next_root(_kvm, NULL, _shared, false); \ + for (_root =3D tdp_mmu_next_root(_kvm, NULL, false); \ _root; \ - _root =3D tdp_mmu_next_root(_kvm, _root, _shared, false)) \ + _root =3D tdp_mmu_next_root(_kvm, _root, false)) \ if (!kvm_lockdep_assert_mmu_lock_held(_kvm, _shared)) { \ } else =20 @@ -891,7 +899,7 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm) * the root must be reachable by mmu_notifiers while it's being * zapped */ - kvm_tdp_mmu_put_root(kvm, root, true); + kvm_tdp_mmu_put_root(kvm, root); } =20 read_unlock(&kvm->mmu_lock); @@ -1500,7 +1508,7 @@ void kvm_tdp_mmu_try_split_huge_pages(struct kvm *kvm, for_each_valid_tdp_mmu_root_yield_safe(kvm, root, slot->as_id, shared) { r =3D tdp_mmu_split_huge_pages_root(kvm, root, start, end, target_level,= shared); if (r) { - kvm_tdp_mmu_put_root(kvm, root, shared); + kvm_tdp_mmu_put_root(kvm, root); break; } } diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h index 733a3aef3a96..20d97aa46c49 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.h +++ b/arch/x86/kvm/mmu/tdp_mmu.h @@ -17,8 +17,7 @@ __must_check static inline bool kvm_tdp_mmu_get_root(stru= ct kvm_mmu_page *root) return refcount_inc_not_zero(&root->tdp_mmu_root_count); } =20 -void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root, - bool shared); +void kvm_tdp_mmu_put_root(struct kvm *kvm, struct kvm_mmu_page *root); =20 bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, gfn_t start, gfn_t end, bool f= lush); bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp); --=20 2.39.1