From patchwork Thu Nov 10 16:48:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 13039008 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 EB4DCC433FE for ; Thu, 10 Nov 2022 16:50:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232704AbiKJQuR (ORCPT ); Thu, 10 Nov 2022 11:50:17 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49198 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232667AbiKJQtx (ORCPT ); Thu, 10 Nov 2022 11:49:53 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C2EC62E1 for ; Thu, 10 Nov 2022 08:48:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668098893; 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; bh=TqTk3iARBWuKOOf8pMxkaVE9+5uAE54PiKz0+D5q5yw=; b=Y9ituNF8eumkab8UnsOwjQlGjTHi5hIb8v+Mo2xRjT1EpHh3DOUGY9dFOaAqwlFXi6NoDY 5ObQG7q97yqK3hojWuSC9/+jKTvgfPHMj+8bqCRtHdXSD8PABawxTHOY5kQjGJbxXI1SVp E2neba09G82+TetZD0eUGKkc1LY2cpk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-605-rhucC4mqN2mKQ3hyMKlxyw-1; Thu, 10 Nov 2022 11:48:12 -0500 X-MC-Unique: rhucC4mqN2mKQ3hyMKlxyw-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 769F4381FA42; Thu, 10 Nov 2022 16:48:09 +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 C4AA040C94AA; Thu, 10 Nov 2022 16:48:08 +0000 (UTC) From: Emanuele Giuseppe Esposito To: qemu-devel@nongnu.org Cc: Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum , =?utf-8?q?Philippe_Mathieu-D?= =?utf-8?q?aud=C3=A9?= , Yanan Wang , kvm@vger.kernel.org, Emanuele Giuseppe Esposito Subject: [PATCH v2 0/3] KVM: allow listener to stop all vcpus before Date: Thu, 10 Nov 2022 11:48:04 -0500 Message-Id: <20221110164807.1306076-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org QEMU needs to perform memslots operations like merging and splitting, and each operation requires more than a single ioctl. Therefore if a vcpu is concurrently reading the same memslots, it could end up reading something that was temporarly deleted. For example, merging two memslots into one would imply: DELETE(m1) DELETE(m2) CREATE(m1+m2) And a vcpu could attempt to read m2 right after it is deleted, but before the new one is created. This approach is 100% QEMU-based. No KVM API modification is involved, but implies that QEMU must make sure no new ioctl is running and all vcpus are stopped. The logic and code are basically taken from David Hildenbrand proposal given a while ago while reviewing a previous attempt where I suggested to solve the above problem directly in KVM by extending its API. This is the original code: https://github.com/davidhildenbrand/qemu/commit/86b1bf546a8d00908e33f7362b0b61e2be8dbb7a I just split the patch in three smaller patches, and used a QemuLockCnt instead of counter + mutex. RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1979276 Emanuele --- v2: * use QemuEvent instead of spinning in ioctl_inhibit_begin * move the blocker API in a separate file and header, so that other accel can use it if they want. David Hildenbrand (1): kvm: Atomic memslot updates Emanuele Giuseppe Esposito (2): accel: introduce accelerator blocker API KVM: keep track of running ioctls accel/accel-blocker.c | 139 +++++++++++++++++++++++++++++++++ accel/kvm/kvm-all.c | 107 ++++++++++++++++++++++--- accel/meson.build | 2 +- hw/core/cpu-common.c | 2 + include/hw/core/cpu.h | 3 + include/sysemu/accel-blocker.h | 45 +++++++++++ include/sysemu/kvm_int.h | 8 ++ 7 files changed, 294 insertions(+), 12 deletions(-) create mode 100644 accel/accel-blocker.c create mode 100644 include/sysemu/accel-blocker.h