From patchwork Fri Oct 18 10:53:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sergio Lopez X-Patchwork-Id: 11198283 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 B62F9913 for ; Fri, 18 Oct 2019 11:07:09 +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 94EB12064A for ; Fri, 18 Oct 2019 11:07:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 94EB12064A 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:38020 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLQ68-0002Uh-Jb for patchwork-qemu-devel@patchwork.kernel.org; Fri, 18 Oct 2019 07:07:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57925) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iLPuc-0006Gr-PY for qemu-devel@nongnu.org; Fri, 18 Oct 2019 06:55:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iLPub-0001sa-2c for qemu-devel@nongnu.org; Fri, 18 Oct 2019 06:55:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53720) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iLPua-0001s1-QU for qemu-devel@nongnu.org; Fri, 18 Oct 2019 06:55:13 -0400 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 mx1.redhat.com (Postfix) with ESMTPS id 0C151877AD3; Fri, 18 Oct 2019 10:55:12 +0000 (UTC) Received: from dritchie.redhat.com (unknown [10.33.36.146]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0AD525D713; Fri, 18 Oct 2019 10:55:02 +0000 (UTC) From: Sergio Lopez To: qemu-devel@nongnu.org Subject: [PATCH v11 13/15] docs/microvm.rst: document the new microvm machine type Date: Fri, 18 Oct 2019 12:53:13 +0200 Message-Id: <20191018105315.27511-14-slp@redhat.com> In-Reply-To: <20191018105315.27511-1-slp@redhat.com> References: <20191018105315.27511-1-slp@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.69]); Fri, 18 Oct 2019 10:55:12 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 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: berrange@redhat.com, ehabkost@redhat.com, Sergio Lopez , mst@redhat.com, lersek@redhat.com, groug@kaod.org, =?utf-8?q?Marc-Andr?= =?utf-8?q?=C3=A9_Lureau?= , marcandre.lureau@gmail.com, kraxel@redhat.com, pbonzini@redhat.com, imammedo@redhat.com, sgarzare@redhat.com, philmd@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" Document the new microvm machine type. Signed-off-by: Sergio Lopez Reviewed-by: Michael S. Tsirkin Reviewed-by: Marc-André Lureau --- docs/microvm.rst | 108 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) create mode 100644 docs/microvm.rst diff --git a/docs/microvm.rst b/docs/microvm.rst new file mode 100644 index 0000000000..aae811a922 --- /dev/null +++ b/docs/microvm.rst @@ -0,0 +1,108 @@ +==================== +microvm Machine Type +==================== + +``microvm`` is a machine type inspired by ``Firecracker`` and +constructed after its machine model. + +It's a minimalist machine type without ``PCI`` nor ``ACPI`` support, +designed for short-lived guests. microvm also establishes a baseline +for benchmarking and optimizing both QEMU and guest operating systems, +since it is optimized for both boot time and footprint. + + +Supported devices +----------------- + +The microvm machine type supports the following devices: + +- ISA bus +- i8259 PIC (optional) +- i8254 PIT (optional) +- MC146818 RTC (optional) +- One ISA serial port (optional) +- LAPIC +- IOAPIC (with kernel-irqchip=split by default) +- kvmclock (if using KVM) +- fw_cfg +- Up to eight virtio-mmio devices (configured by the user) + + +Limitations +----------- + +Currently, microvm does *not* support the following features: + + - PCI-only devices. + - Hotplug of any kind. + - Live migration across QEMU versions. + + +Using the microvm machine type +------------------------------ + +Machine-specific options +~~~~~~~~~~~~~~~~~~~~~~~~ + +It supports the following machine-specific options: + +- microvm.x-option-roms=bool (Set off to disable loading option ROMs) +- microvm.pit=OnOffAuto (Enable i8254 PIT) +- microvm.isa-serial=bool (Set off to disable the instantiation an ISA serial port) +- microvm.pic=OnOffAuto (Enable i8259 PIC) +- microvm.rtc=OnOffAuto (Enable MC146818 RTC) +- microvm.auto-kernel-cmdline=bool (Set off to disable adding virtio-mmio devices to the kernel cmdline) + + +Boot options +~~~~~~~~~~~~ + +By default, microvm uses ``qboot`` as its BIOS, to obtain better boot +times, but it's also compatible with ``SeaBIOS``. + +As no current FW is able to boot from a block device using +``virtio-mmio`` as its transport, a microvm-based VM needs to be run +using a host-side kernel and, optionally, an initrd image. + + +Running a microvm-based VM +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +By default, microvm aims for maximum compatibility, enabling both +legacy and non-legacy devices. In this example, a VM is created +without passing any additional machine-specific option, using the +legacy ``ISA serial`` device as console:: + + $ qemu-system-x86_64 -M microvm \ + -enable-kvm -cpu host -m 512m -smp 2 \ + -kernel vmlinux -append "earlyprintk=ttyS0 console=ttyS0 root=/dev/vda" \ + -nodefaults -no-user-config -nographic \ + -serial stdio \ + -drive id=test,file=test.img,format=raw,if=none \ + -device virtio-blk-device,drive=test \ + -netdev tap,id=tap0,script=no,downscript=no \ + -device virtio-net-device,netdev=tap0 + +While the example above works, you might be interested in reducing the +footprint further by disabling some legacy devices. If you're using +``KVM``, you can disable the ``RTC``, making the Guest rely on +``kvmclock`` exclusively. Additionally, if your host's CPUs have the +``TSC_DEADLINE`` feature, you can also disable both the i8259 PIC and +the i8254 PIT (make sure you're also emulating a CPU with such feature +in the guest). + +This is an example of a VM with all optional legacy features +disabled:: + + $ qemu-system-x86_64 \ + -M microvm,x-option-roms=off,pit=off,pic=off,isa-serial=off,rtc=off \ + -enable-kvm -cpu host -m 512m -smp 2 \ + -kernel vmlinux -append "console=hvc0 root=/dev/vda" \ + -nodefaults -no-user-config -nographic \ + -chardev stdio,id=virtiocon0 \ + -device virtio-serial-device \ + -device virtconsole,chardev=virtiocon0 \ + -drive id=test,file=test.img,format=raw,if=none \ + -device virtio-blk-device,drive=test \ + -netdev tap,id=tap0,script=no,downscript=no \ + -device virtio-net-device,netdev=tap0