From patchwork Wed May 20 12:31:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 282300 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08315C433DF for ; Wed, 20 May 2020 12:33:22 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C9D8B20756 for ; Wed, 20 May 2020 12:33:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QMTBzU13" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C9D8B20756 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50616 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jbNuS-0006GW-Uv for qemu-devel@archiver.kernel.org; Wed, 20 May 2020 08:33:20 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40188) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jbNtT-00044Z-No for qemu-devel@nongnu.org; Wed, 20 May 2020 08:32:19 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:55060 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jbNtS-0007RI-S8 for qemu-devel@nongnu.org; Wed, 20 May 2020 08:32:19 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589977937; 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=csTCzjprRmlnuhs1t5G0bRckObBhYBDq2SaPlfd5uBA=; b=QMTBzU13JTtqZZkHrQhlJe8XI/8mZEEERMwVUMcar1ssHizRnnWzP73kf5WUFOHTvG0BYg grKSL+5v0sEkFpYaGAkoobUMdub+wQo0HRkYXeN5H6C51l3djXPr28T5nWluy1RwQo+BgZ 3UqdehcZVLyWo/5RmJwpjYlAK/ViQdo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-404-RxSYxRzzPT-tNfKEDBm5TQ-1; Wed, 20 May 2020 08:32:11 -0400 X-MC-Unique: RxSYxRzzPT-tNfKEDBm5TQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2E62A464; Wed, 20 May 2020 12:32:10 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-76.ams2.redhat.com [10.36.113.76]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4F1146EA21; Wed, 20 May 2020 12:32:08 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v2 01/19] exec: Introduce ram_block_discard_(disable|require)() Date: Wed, 20 May 2020 14:31:34 +0200 Message-Id: <20200520123152.60527-2-david@redhat.com> In-Reply-To: <20200520123152.60527-1-david@redhat.com> References: <20200520123152.60527-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Received-SPF: pass client-ip=205.139.110.120; envelope-from=david@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/19 22:48:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , kvm@vger.kernel.org, "Michael S . Tsirkin" , David Hildenbrand , "Dr . David Alan Gilbert" , qemu-s390x@nongnu.org, Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" We want to replace qemu_balloon_inhibit() by something more generic. Especially, we want to make sure that technologies that really rely on RAM block discards to work reliably to run mutual exclusive with technologies that effectively break it. E.g., vfio will usually pin all guest memory, turning the virtio-balloon basically useless and make the VM consume more memory than reported via the balloon. While the balloon is special already (=> no guarantees, same behavior possible afer reboots and with huge pages), this will be different, especially, with virtio-mem. Let's implement a way such that we can make both types of technology run mutually exclusive. We'll convert existing balloon inhibitors in successive patches and add some new ones. Add the check to qemu_balloon_is_inhibited() for now. We might want to make virtio-balloon an acutal inhibitor in the future - however, that requires more thought to not break existing setups. Reviewed-by: Dr. David Alan Gilbert Cc: "Michael S. Tsirkin" Cc: Richard Henderson Cc: Paolo Bonzini Signed-off-by: David Hildenbrand --- balloon.c | 3 ++- exec.c | 52 +++++++++++++++++++++++++++++++++++++++++++ include/exec/memory.h | 41 ++++++++++++++++++++++++++++++++++ 3 files changed, 95 insertions(+), 1 deletion(-) diff --git a/balloon.c b/balloon.c index f104b42961..5fff79523a 100644 --- a/balloon.c +++ b/balloon.c @@ -40,7 +40,8 @@ static int balloon_inhibit_count; bool qemu_balloon_is_inhibited(void) { - return atomic_read(&balloon_inhibit_count) > 0; + return atomic_read(&balloon_inhibit_count) > 0 || + ram_block_discard_is_disabled(); } void qemu_balloon_inhibit(bool state) diff --git a/exec.c b/exec.c index 5162f0d12f..648a3ea7f2 100644 --- a/exec.c +++ b/exec.c @@ -4049,4 +4049,56 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root) } } +/* + * If positive, discarding RAM is disabled. If negative, discarding RAM is + * required to work and cannot be disabled. + */ +static int ram_block_discard_disabled; + +int ram_block_discard_disable(bool state) +{ + int old; + + if (!state) { + atomic_dec(&ram_block_discard_disabled); + return 0; + } + + do { + old = atomic_read(&ram_block_discard_disabled); + if (old < 0) { + return -EBUSY; + } + } while (atomic_cmpxchg(&ram_block_discard_disabled, old, old + 1) != old); + return 0; +} + +int ram_block_discard_require(bool state) +{ + int old; + + if (!state) { + atomic_inc(&ram_block_discard_disabled); + return 0; + } + + do { + old = atomic_read(&ram_block_discard_disabled); + if (old > 0) { + return -EBUSY; + } + } while (atomic_cmpxchg(&ram_block_discard_disabled, old, old - 1) != old); + return 0; +} + +bool ram_block_discard_is_disabled(void) +{ + return atomic_read(&ram_block_discard_disabled) > 0; +} + +bool ram_block_discard_is_required(void) +{ + return atomic_read(&ram_block_discard_disabled) < 0; +} + #endif diff --git a/include/exec/memory.h b/include/exec/memory.h index e000bd2f97..4e5da78f0e 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -2463,6 +2463,47 @@ static inline MemOp devend_memop(enum device_endian end) } #endif +/* + * Inhibit technologies that require discarding of pages in RAM blocks, e.g., + * to manage the actual amount of memory consumed by the VM (then, the memory + * provided by RAM blocks might be bigger than the desired memory consumption). + * This *must* be set if: + * - Discarding parts of a RAM blocks does not result in the change being + * reflected in the VM and the pages getting freed. + * - All memory in RAM blocks is pinned or duplicated, invaldiating any previous + * discards blindly. + * - Discarding parts of a RAM blocks will result in integrity issues (e.g., + * encrypted VMs). + * Technologies that only temporarily pin the current working set of a + * driver are fine, because we don't expect such pages to be discarded + * (esp. based on guest action like balloon inflation). + * + * This is *not* to be used to protect from concurrent discards (esp., + * postcopy). + * + * Returns 0 if successful. Returns -EBUSY if a technology that relies on + * discards to work reliably is active. + */ +int ram_block_discard_disable(bool state); + +/* + * Inhibit technologies that disable discarding of pages in RAM blocks. + * + * Returns 0 if successful. Returns -EBUSY if discards are already set to + * broken. + */ +int ram_block_discard_require(bool state); + +/* + * Test if discarding of memory in ram blocks is disabled. + */ +bool ram_block_discard_is_disabled(void); + +/* + * Test if discarding of memory in ram blocks is required to work reliably. + */ +bool ram_block_discard_is_required(void); + #endif #endif