From patchwork Tue Aug 11 10:27:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 11709037 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D2BE9618 for ; Tue, 11 Aug 2020 10:27:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BAFD320756 for ; Tue, 11 Aug 2020 10:27:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597141659; bh=9Romhf292P/7ZD0l5gS6HnWmQI7XdzkZhvz1lKd/kss=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LoFRQfDF0Wa6gjhfsJbdGSg8NGGhAXT1rwEiINcykdMJNacX1qL33myXvVCrdl5j9 +1H1OglzERm0Jl9/Zrw77j70qFAycHECLvuURR4hC8K+pdFoJU3QkeYuO7knY1JOQP XBSepG3lDkcOdXCkF2EH8HCZ6Qws2ohLmwC/vXZ4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728662AbgHKK1i (ORCPT ); Tue, 11 Aug 2020 06:27:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:54544 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728650AbgHKK1h (ORCPT ); Tue, 11 Aug 2020 06:27:37 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 57C602076B; Tue, 11 Aug 2020 10:27:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597141656; bh=9Romhf292P/7ZD0l5gS6HnWmQI7XdzkZhvz1lKd/kss=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aAlG44Q2Txjplxll/ncPm0p5mbaNu1HTyfSnYzKxvkVBKedsl0inc+1EdrfsYIwiT DBJFfyBY3IYVYvGJkpJ+rXRDPjIajafW8A0T6lOnQGz8wPjGWzs2zF8/GIshW1lLN2 JE37Fg/E48IslKJ8Mi3OvZgns2UgYJkmqX3mj8c4= From: Will Deacon To: kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Will Deacon , Marc Zyngier , Suzuki K Poulose , James Morse , Thomas Bogendoerfer , Paul Mackerras , Paolo Bonzini , Sean Christopherson , stable@vger.kernel.org Subject: [PATCH 2/2] KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set Date: Tue, 11 Aug 2020 11:27:25 +0100 Message-Id: <20200811102725.7121-3-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200811102725.7121-1-will@kernel.org> References: <20200811102725.7121-1-will@kernel.org> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org When an MMU notifier call results in unmapping a range that spans multiple PGDs, we end up calling into cond_resched_lock() when crossing a PGD boundary, since this avoids running into RCU stalls during VM teardown. Unfortunately, if the VM is destroyed as a result of OOM, then blocking is not permitted and the call to the scheduler triggers the following BUG(): | BUG: sleeping function called from invalid context at arch/arm64/kvm/mmu.c:394 | in_atomic(): 1, irqs_disabled(): 0, non_block: 1, pid: 36, name: oom_reaper | INFO: lockdep is turned off. | CPU: 3 PID: 36 Comm: oom_reaper Not tainted 5.8.0 #1 | Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 | Call trace: | dump_backtrace+0x0/0x284 | show_stack+0x1c/0x28 | dump_stack+0xf0/0x1a4 | ___might_sleep+0x2bc/0x2cc | unmap_stage2_range+0x160/0x1ac | kvm_unmap_hva_range+0x1a0/0x1c8 | kvm_mmu_notifier_invalidate_range_start+0x8c/0xf8 | __mmu_notifier_invalidate_range_start+0x218/0x31c | mmu_notifier_invalidate_range_start_nonblock+0x78/0xb0 | __oom_reap_task_mm+0x128/0x268 | oom_reap_task+0xac/0x298 | oom_reaper+0x178/0x17c | kthread+0x1e4/0x1fc | ret_from_fork+0x10/0x30 Use the new 'flags' argument to kvm_unmap_hva_range() to ensure that we only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is set in the notifier flags. Cc: Fixes: 8b3405e345b5 ("kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd") Cc: Marc Zyngier Cc: Suzuki K Poulose Cc: James Morse Signed-off-by: Will Deacon Reviewed-by: Suzuki K Poulose --- arch/arm64/kvm/mmu.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 5f6b35c33618..bd47f06739d6 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -365,7 +365,8 @@ static void unmap_stage2_p4ds(struct kvm *kvm, pgd_t *pgd, * destroying the VM), otherwise another faulting VCPU may come in and mess * with things behind our backs. */ -static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) +static void __unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size, + bool may_block) { pgd_t *pgd; phys_addr_t addr = start, end = start + size; @@ -390,11 +391,16 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) * If the range is too large, release the kvm->mmu_lock * to prevent starvation and lockup detector warnings. */ - if (next != end) + if (may_block && next != end) cond_resched_lock(&kvm->mmu_lock); } while (pgd++, addr = next, addr != end); } +static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) +{ + __unmap_stage2_range(kvm, start, size, true); +} + static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd, phys_addr_t addr, phys_addr_t end) { @@ -2198,7 +2204,10 @@ static int handle_hva_to_gpa(struct kvm *kvm, static int kvm_unmap_hva_handler(struct kvm *kvm, gpa_t gpa, u64 size, void *data) { - unmap_stage2_range(kvm, gpa, size); + unsigned flags = *(unsigned *)data; + bool may_block = flags & MMU_NOTIFIER_RANGE_BLOCKABLE; + + __unmap_stage2_range(kvm, gpa, size, may_block); return 0; } @@ -2209,7 +2218,7 @@ int kvm_unmap_hva_range(struct kvm *kvm, return 0; trace_kvm_unmap_hva_range(start, end); - handle_hva_to_gpa(kvm, start, end, &kvm_unmap_hva_handler, NULL); + handle_hva_to_gpa(kvm, start, end, &kvm_unmap_hva_handler, &flags); return 0; }