From mboxrd@z Thu Jan 1 00:00:00 1970 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 5BD21FA3744 for ; Thu, 27 Oct 2022 22:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235404AbiJ0WTm (ORCPT ); Thu, 27 Oct 2022 18:19:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235368AbiJ0WTj (ORCPT ); Thu, 27 Oct 2022 18:19:39 -0400 Received: from out2.migadu.com (out2.migadu.com [188.165.223.204]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5CABA65C3 for ; Thu, 27 Oct 2022 15:19:31 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1666909170; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SGgezeaRpwTbMJIwssPR+7+RFNLpIEtsfVUv+WQJPCY=; b=M/EoevzFfiPGlFnffXiUm4is7ZrRno9Or5lwGUFDOPAWGe38FC7h7OdzBokBUyNaDZzy+A TtHP6rUmLK9ciWOHrNxMeauNfrxoYQKd70YjzVq4VUTSPz25//n+LI6oIg54E5SFLFqWPn lONjpWUmsIvEgQO++wRLFrOVU4CMt+w= From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Reiji Watanabe , Ricardo Koller , David Matlack , Quentin Perret , Ben Gardon , Gavin Shan , Peter Xu , Will Deacon , Sean Christopherson , kvmarm@lists.linux.dev, Oliver Upton Subject: [PATCH v3 08/15] KVM: arm64: Protect stage-2 traversal with RCU Date: Thu, 27 Oct 2022 22:17:45 +0000 Message-Id: <20221027221752.1683510-9-oliver.upton@linux.dev> In-Reply-To: <20221027221752.1683510-1-oliver.upton@linux.dev> References: <20221027221752.1683510-1-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The use of RCU is necessary to safely change the stage-2 page tables in parallel. Acquire and release the RCU read lock when traversing the page tables. Use the _raw() flavor of rcu_dereference when changes to the page tables are otherwise protected from parallel software walkers (e.g. holding the write lock). Signed-off-by: Oliver Upton --- arch/arm64/include/asm/kvm_pgtable.h | 41 ++++++++++++++++++++++++++++ arch/arm64/kvm/hyp/pgtable.c | 10 ++++++- 2 files changed, 50 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index e70cf57b719e..d1859e8550df 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -37,6 +37,13 @@ static inline u64 kvm_get_parange(u64 mmfr0) typedef u64 kvm_pte_t; +/* + * RCU cannot be used in a non-kernel context such as the hyp. As such, page + * table walkers used in hyp do not call into RCU and instead use other + * synchronization mechanisms (such as a spinlock). + */ +#if defined(__KVM_NVHE_HYPERVISOR__) || defined(__KVM_VHE_HYPERVISOR__) + typedef kvm_pte_t *kvm_pteref_t; static inline kvm_pte_t *kvm_dereference_pteref(kvm_pteref_t pteref, bool shared) @@ -44,6 +51,40 @@ static inline kvm_pte_t *kvm_dereference_pteref(kvm_pteref_t pteref, bool shared return pteref; } +static inline void kvm_pgtable_walk_begin(void) {} +static inline void kvm_pgtable_walk_end(void) {} + +static inline bool kvm_pgtable_walk_lock_held(void) +{ + return true; +} + +#else + +typedef kvm_pte_t __rcu *kvm_pteref_t; + +static inline kvm_pte_t *kvm_dereference_pteref(kvm_pteref_t pteref, bool shared) +{ + return rcu_dereference_check(pteref, shared); +} + +static inline void kvm_pgtable_walk_begin(void) +{ + rcu_read_lock(); +} + +static inline void kvm_pgtable_walk_end(void) +{ + rcu_read_unlock(); +} + +static inline bool kvm_pgtable_walk_lock_held(void) +{ + return rcu_read_lock_held(); +} + +#endif + #define KVM_PTE_VALID BIT(0) #define KVM_PTE_ADDR_MASK GENMASK(47, PAGE_SHIFT) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index c4d103889a62..5bab932aeaec 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -171,6 +171,9 @@ static int kvm_pgtable_visitor_cb(struct kvm_pgtable_walk_data *data, enum kvm_pgtable_walk_flags visit) { struct kvm_pgtable_walker *walker = data->walker; + + /* Ensure the appropriate lock is held (e.g. RCU lock for stage-2 MMU) */ + WARN_ON_ONCE(kvm_pgtable_walk_shared(ctx) && !kvm_pgtable_walk_lock_held()); return walker->cb(ctx, visit); } @@ -281,8 +284,13 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, .end = PAGE_ALIGN(walk_data.addr + size), .walker = walker, }; + int r; + + kvm_pgtable_walk_begin(); + r = _kvm_pgtable_walk(pgt, &walk_data); + kvm_pgtable_walk_end(); - return _kvm_pgtable_walk(pgt, &walk_data); + return r; } struct leaf_walk_data { -- 2.38.1.273.g43a17bfeac-goog