From: Peter Maydell Date: Thu, 12 Nov 2020 14:40:38 +0000 (+0000) Subject: docs: Move microvm.rst into the system manual X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e8eee8d3d90690b73caac6b0059ad02ed1f170e6;p=qemu.git docs: Move microvm.rst into the system manual Now that target-i386.rst has a place to list documentation of machines other than the 'pc' machine, we have a place we can move the microvm documentation to. Signed-off-by: Peter Maydell Reviewed-by: Alex Bennée --- diff --git a/docs/microvm.rst b/docs/microvm.rst deleted file mode 100644 index fcf41fc1f6..0000000000 --- a/docs/microvm.rst +++ /dev/null @@ -1,129 +0,0 @@ -==================== -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 - - -Triggering a guest-initiated shut down -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -As the microvm machine type includes just a small set of system -devices, some x86 mechanisms for rebooting or shutting down the -system, like sending a key sequence to the keyboard or writing to an -ACPI register, doesn't have any effect in the VM. - -The recommended way to trigger a guest-initiated shut down is by -generating a ``triple-fault``, which will cause the VM to initiate a -reboot. Additionally, if the ``-no-reboot`` argument is present in the -command line, QEMU will detect this event and terminate its own -execution gracefully. - -Linux does support this mechanism, but by default will only be used -after other options have been tried and failed, causing the reboot to -be delayed by a small number of seconds. It's possible to instruct it -to try the triple-fault mechanism first, by adding ``reboot=t`` to the -kernel's command line. diff --git a/docs/system/i386/microvm.rst b/docs/system/i386/microvm.rst new file mode 100644 index 0000000000..1675e37d3e --- /dev/null +++ b/docs/system/i386/microvm.rst @@ -0,0 +1,128 @@ +'microvm' virtual platform (``microvm``) +======================================== + +``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 + + +Triggering a guest-initiated shut down +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As the microvm machine type includes just a small set of system +devices, some x86 mechanisms for rebooting or shutting down the +system, like sending a key sequence to the keyboard or writing to an +ACPI register, doesn't have any effect in the VM. + +The recommended way to trigger a guest-initiated shut down is by +generating a ``triple-fault``, which will cause the VM to initiate a +reboot. Additionally, if the ``-no-reboot`` argument is present in the +command line, QEMU will detect this event and terminate its own +execution gracefully. + +Linux does support this mechanism, but by default will only be used +after other options have been tried and failed, causing the reboot to +be delayed by a small number of seconds. It's possible to instruct it +to try the triple-fault mechanism first, by adding ``reboot=t`` to the +kernel's command line. diff --git a/docs/system/target-i386.rst b/docs/system/target-i386.rst index 1612ddba90..22ba5ce2c0 100644 --- a/docs/system/target-i386.rst +++ b/docs/system/target-i386.rst @@ -16,6 +16,7 @@ Board-specific documentation .. toctree:: :maxdepth: 1 + i386/microvm i386/pc .. include:: cpu-models-x86.rst.inc