From nobody Wed Nov 12 13:35:33 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1570718481; cv=none; d=zoho.com; s=zohoarc; b=KU6v2L16dvfMjnPiJOhNTpNsb28zo7e+ut6TFliQUIQR4kenNqHhdKTDmamm4kkUNQDOcm6OPVEmj/3ZY/Y6UhOWyWHbcqeQiKPnkwMeoLrpkprLlLDItkBLrEZIkAfNWN4JBHQiRUaHwlAPsT5JSfHLRdQx2rLxWzXlLZnV0P0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1570718481; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=mYxGhSk2FI5FlSdUQAgSX7f85ID31jXa8JqF8dkV/lw=; b=iegXl5tSaev3H+KZcm9grkSK2benpvyQYEPc1E4/3E0AXkIpXu/AbRqpw70SMztDwWUtnJzcbNwiEl9aSbdJKhCkxWjiwnhkHtmuKl3A59GHLOcPEQNW+vpp4OPpIDFpox2J8Z2grfJlGuUPfV/KUNvfnPTkQqwXy/fbfcH3qxE= ARC-Authentication-Results: i=1; mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1570718481798620.9067107266643; Thu, 10 Oct 2019 07:41:21 -0700 (PDT) Received: from localhost ([::1]:40490 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIZd0-0001xL-2c for importer@patchew.org; Thu, 10 Oct 2019 10:41:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52683) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iIZXS-0002is-U8 for qemu-devel@nongnu.org; Thu, 10 Oct 2019 10:35:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iIZXR-00026u-Gc for qemu-devel@nongnu.org; Thu, 10 Oct 2019 10:35:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36741) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iIZXR-00025x-8L for qemu-devel@nongnu.org; Thu, 10 Oct 2019 10:35:33 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7E11B18C4262; Thu, 10 Oct 2019 14:35:32 +0000 (UTC) Received: from dritchie.redhat.com (unknown [10.33.36.122]) by smtp.corp.redhat.com (Postfix) with ESMTP id CDA7560BE1; Thu, 10 Oct 2019 14:35:24 +0000 (UTC) From: Sergio Lopez To: qemu-devel@nongnu.org Subject: [PATCH v8 13/15] docs/microvm.rst: document the new microvm machine type Date: Thu, 10 Oct 2019 16:31:24 +0200 Message-Id: <20191010143125.67246-15-slp@redhat.com> In-Reply-To: <20191010143125.67246-1-slp@redhat.com> References: <20191010143125.67246-1-slp@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.62]); Thu, 10 Oct 2019 14:35:32 +0000 (UTC) Content-Transfer-Encoding: quoted-printable 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: ehabkost@redhat.com, Sergio Lopez , mst@redhat.com, lersek@redhat.com, kraxel@redhat.com, pbonzini@redhat.com, imammedo@redhat.com, sgarzare@redhat.com, philmd@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" Document the new microvm machine type. Signed-off-by: Sergio Lopez Reviewed-by: Michael S. Tsirkin --- docs/microvm.rst | 98 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 docs/microvm.rst diff --git a/docs/microvm.rst b/docs/microvm.rst new file mode 100644 index 0000000000..dc36ecf7c3 --- /dev/null +++ b/docs/microvm.rst @@ -0,0 +1,98 @@ +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Microvm Machine Type +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Microvm is a machine type inspired by ``Firecracker`` and constructed +after the 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=3Dsplit by default) +- kvmclock (if using KVM) +- fw_cfg +- Up to eight virtio-mmio devices (configured by the user) + + +Using the microvm machine type +------------------------------ + +Machine-specific options +~~~~~~~~~~~~~~~~~~~~~~~~ + +It supports the following machine-specific options: + +- microvm.x-option-roms=3Dbool (Set off to disable loading option ROMs) +- microvm.pit=3DOnOffAuto (Enable i8254 PIT) +- microvm.isa-serial=3Dbool (Set off to disable the instantiation an ISA s= erial port) +- microvm.pic=3DOnOffAuto (Enable i8259 PIC) +- microvm.rtc=3DOnOffAuto (Enable MC146818 RTC) +- microvm.auto-kernel-cmdline=3Dbool (Set off to disable adding virtio-mmi= o 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=3DttyS0 console=3DttyS0 root=3D/= dev/vda" \ + -nodefaults -no-user-config -nographic \ + -serial stdio \ + -drive id=3Dtest,file=3Dtest.img,format=3Draw,if=3Dnone \ + -device virtio-blk-device,drive=3Dtest \ + -netdev tap,id=3Dtap0,script=3Dno,downscript=3Dno \ + -device virtio-net-device,netdev=3Dtap0 + +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=3Doff,pit=3Doff,pic=3Doff,isa-serial=3Doff,r= tc=3Doff \ + -enable-kvm -cpu host -m 512m -smp 2 \ + -kernel vmlinux -append "console=3Dhvc0 root=3D/dev/vda" \ + -nodefaults -no-user-config -nographic \ + -chardev stdio,id=3Dvirtiocon0,server \ + -device virtio-serial-device \ + -device virtconsole,chardev=3Dvirtiocon0 \ + -drive id=3Dtest,file=3Dtest.img,format=3Draw,if=3Dnone \ + -device virtio-blk-device,drive=3Dtest \ + -netdev tap,id=3Dtap0,script=3Dno,downscript=3Dno \ + -device virtio-net-device,netdev=3Dtap0 --=20 2.21.0