Cc: Sergio Lopez <s...@redhat.com>
Suggested-by: Stefan Hajnoczi <stefa...@gmail.com>
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
docs/system/i386/microvm.rst | 52 +++++++++++++-----------------------
1 file changed, 19 insertions(+), 33 deletions(-)
diff --git a/docs/system/i386/microvm.rst b/docs/system/i386/microvm.rst
index 1675e37d3e73..2baa68719c1d 100644
--- a/docs/system/i386/microvm.rst
+++ b/docs/system/i386/microvm.rst
@@ -4,10 +4,10 @@
``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.
+It's a minimalist machine type 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
@@ -24,7 +24,9 @@ The microvm machine type supports the following devices:
- IOAPIC (with kernel-irqchip=split by default)
- kvmclock (if using KVM)
- fw_cfg
-- Up to eight virtio-mmio devices (configured by the user)
+- Up to 24 virtio-mmio devices (configured by the user).
+- PCIe devices (optional).
+- USB devices (optional).
Limitations
@@ -32,7 +34,6 @@ Limitations
Currently, microvm does *not* support the following features:
-- PCI-only devices.
- Hotplug of any kind.
- Live migration across QEMU versions.
@@ -50,18 +51,24 @@ It supports the following machine-specific options:
- 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)
+- microvm.acpi=OnOff (Enable ACPI support, default On)
+- microvm.auto-kernel-cmdline=bool (Set off to disable adding
+ virtio-mmio devices to the kernel cmdline, enabling ACPI support
+ disables this too).
+- microvm.pcie=OnOff (Enable PCIe host adapter, default Off)
+- microvm.usb=OnOff (Enable USB host adapter, default Off)
+- microvm.ioapic2=OnOff (Enable second IOAPIC for virtio-mmio devices,
+ required for more than eight virtio-mmio devices, default On)
Boot options
~~~~~~~~~~~~
-By default, microvm uses ``qboot`` as its BIOS, to obtain better boot
-times, but it's also compatible with ``SeaBIOS``.
+By default, microvm uses ``SeaBIOS`` as its firmware. ``SeaBIOS``
+supports booting from virtio-mmio devices.
-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.
+edk2 has full support for microvm, including support for the PCIe host
+adapter. so you can boot from both virtio-mmio and PCIe devices.
Running a microvm-based VM
@@ -105,24 +112,3 @@ disabled::
-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.
--
2.39.1
