From patchwork Fri Nov 18 18:22:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 13048575 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 16262C4332F for ; Fri, 18 Nov 2022 18:24:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=04hcpeL2eLyboJAQLdgFy8efFmltyMhx2C5ac0TBvNc=; b=A65dys4hWKc41b CdjMn8Z7jhoSZC1nsY2uMCYbo9tD3FrWLYGFl9w1aAYKWFswA/lIo30Q8MRAUDW91dpxB5fEFnVZQ qjVAQqZUBUaLABya+1kMBupyhQ0UbKzMGhTlKwFxAX3OR/fP0pPc5eafJUOJW8Q95uAcI738vsO12 S+Exh9VChkCUs8vMlmsbrOECU8hbFM1nMaxh0thgz+QEYrak9KdHnEf6ShoFHt9xpO6dsj1msIIjx pERCsv7BWjHXIynzI7bTHi3vxLNgdjy+xU1JbKvfYv1KsUrxFwUyB64GE2Umv6Ja1faJMn8D6UfbB ARmHlYFwADv7WkCTWKkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ow611-006RWc-6O; Fri, 18 Nov 2022 18:23:03 +0000 Received: from out2.migadu.com ([2001:41d0:2:aacc::]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ow60e-006R6u-6B for linux-arm-kernel@lists.infradead.org; Fri, 18 Nov 2022 18:22:42 +0000 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=1668795758; 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=+uOM/Fua4rhDVOWefaZ8Uq5AA7UeFgjxJb3kFrB+tz4=; b=EI93hjYHkqlernG2+yC6o8UByESVp2FCWuzQD0gzXgeNCSKZPJ9WCc3OrNqzHbk3vz1q+B RU7LXauCNfP2WenYN272ma1Mww+UaS1WDm2Hm3qtzpIv7jIUBtlUFQgeCeEtCXM5141r/5 82I1DTf2dYq5ORX4Hog6LQXJfhtql7I= From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Oliver Upton , Catalin Marinas , Will Deacon Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, kvmarm@lists.linux.dev, Marek Szyprowski , linux-kernel@vger.kernel.org Subject: [PATCH v4 2/3] KVM: arm64: Don't acquire RCU read lock for exclusive table walks Date: Fri, 18 Nov 2022 18:22:21 +0000 Message-Id: <20221118182222.3932898-3-oliver.upton@linux.dev> In-Reply-To: <20221118182222.3932898-1-oliver.upton@linux.dev> References: <20221118182222.3932898-1-oliver.upton@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221118_102240_418031_EA19D672 X-CRM114-Status: GOOD ( 10.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Marek reported a BUG resulting from the recent parallel faults changes, as the hyp stage-1 map walker attempted to allocate table memory while holding the RCU read lock: BUG: sleeping function called from invalid context at include/linux/sched/mm.h:274 in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper/0 preempt_count: 0, expected: 0 RCU nest depth: 1, expected: 0 2 locks held by swapper/0/1: #0: ffff80000a8a44d0 (kvm_hyp_pgd_mutex){+.+.}-{3:3}, at: __create_hyp_mappings+0x80/0xc4 #1: ffff80000a927720 (rcu_read_lock){....}-{1:2}, at: kvm_pgtable_walk+0x0/0x1f4 CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc3+ #5918 Hardware name: Raspberry Pi 3 Model B (DT) Call trace: dump_backtrace.part.0+0xe4/0xf0 show_stack+0x18/0x40 dump_stack_lvl+0x8c/0xb8 dump_stack+0x18/0x34 __might_resched+0x178/0x220 __might_sleep+0x48/0xa0 prepare_alloc_pages+0x178/0x1a0 __alloc_pages+0x9c/0x109c alloc_page_interleave+0x1c/0xc4 alloc_pages+0xec/0x160 get_zeroed_page+0x1c/0x44 kvm_hyp_zalloc_page+0x14/0x20 hyp_map_walker+0xd4/0x134 kvm_pgtable_visitor_cb.isra.0+0x38/0x5c __kvm_pgtable_walk+0x1a4/0x220 kvm_pgtable_walk+0x104/0x1f4 kvm_pgtable_hyp_map+0x80/0xc4 __create_hyp_mappings+0x9c/0xc4 kvm_mmu_init+0x144/0x1cc kvm_arch_init+0xe4/0xef4 kvm_init+0x3c/0x3d0 arm_init+0x20/0x30 do_one_initcall+0x74/0x400 kernel_init_freeable+0x2e0/0x350 kernel_init+0x24/0x130 ret_from_fork+0x10/0x20 Since the hyp stage-1 table walkers are serialized by kvm_hyp_pgd_mutex, RCU protection really doesn't add anything. Don't acquire the RCU read lock for an exclusive walk. Reported-by: Marek Szyprowski Signed-off-by: Oliver Upton --- arch/arm64/include/asm/kvm_pgtable.h | 14 ++++++++------ arch/arm64/kvm/hyp/pgtable.c | 4 ++-- 2 files changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index f23af693e3c5..4b6b52ebc11c 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -229,8 +229,8 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke return pteref; } -static inline void kvm_pgtable_walk_begin(void) {} -static inline void kvm_pgtable_walk_end(void) {} +static inline void kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker) {} +static inline void kvm_pgtable_walk_end(struct kvm_pgtable_walker *walker) {} static inline bool kvm_pgtable_walk_lock_held(void) { @@ -247,14 +247,16 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke return rcu_dereference_check(pteref, !(walker->flags & KVM_PGTABLE_WALK_SHARED)); } -static inline void kvm_pgtable_walk_begin(void) +static inline void kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker) { - rcu_read_lock(); + if (walker->flags & KVM_PGTABLE_WALK_SHARED) + rcu_read_lock(); } -static inline void kvm_pgtable_walk_end(void) +static inline void kvm_pgtable_walk_end(struct kvm_pgtable_walker *walker) { - rcu_read_unlock(); + if (walker->flags & KVM_PGTABLE_WALK_SHARED) + rcu_read_unlock(); } static inline bool kvm_pgtable_walk_lock_held(void) diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index b5b91a882836..d6f3753cb87e 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -289,9 +289,9 @@ int kvm_pgtable_walk(struct kvm_pgtable *pgt, u64 addr, u64 size, }; int r; - kvm_pgtable_walk_begin(); + kvm_pgtable_walk_begin(walker); r = _kvm_pgtable_walk(pgt, &walk_data); - kvm_pgtable_walk_end(); + kvm_pgtable_walk_end(walker); return r; }