351 lines
10 KiB
ReStructuredText
351 lines
10 KiB
ReStructuredText
.. _kernel-parameters:
|
|
|
|
ACRN Kernel Parameters
|
|
######################
|
|
|
|
Generic Kernel Parameters
|
|
*************************
|
|
|
|
A number of kernel parameters control the behavior of ACRN-based systems. Some
|
|
are applicable to the Service VM kernel, others to the User VM
|
|
kernel, and some are applicable to both.
|
|
|
|
This section focuses on generic parameters from the Linux kernel which are
|
|
relevant for configuring or debugging ACRN-based systems.
|
|
|
|
.. list-table::
|
|
:header-rows: 1
|
|
:widths: 10,10,50,30
|
|
|
|
* - Parameter
|
|
- Used in Service VM or User VM
|
|
- Description
|
|
- Usage Example
|
|
|
|
* - ``module_blacklist``
|
|
- Service VM
|
|
- A comma-separated list of modules that should not be loaded.
|
|
Useful to debug or work
|
|
around issues related to specific modules.
|
|
- ::
|
|
|
|
module_blacklist=dwc3_pci
|
|
|
|
* - ``no_timer_check``
|
|
- Service VM, User VM
|
|
- Disables the code that tests for broken timer IRQ sources.
|
|
- ::
|
|
|
|
no_timer_check
|
|
|
|
* - ``console``
|
|
- Service VM, User VM
|
|
- Output console device and options.
|
|
|
|
``tty<n>``
|
|
Use the virtual console device <n>.
|
|
|
|
``ttyS<n>[,options]``
|
|
Use the specified serial port and options. Default options are
|
|
``9600n8`` meaning 9600 baud, no parity, 8 bits. Options are of the form *bbbbpnf*,
|
|
where:
|
|
|
|
| *bbbb* is baud rate, for example, 9600
|
|
| *p* is parity, one of ``n``, ``o``, or ``e`` (for none, odd, or even)
|
|
| *n* is number of bits (typically 8)
|
|
| *f* is flow control (``r`` for RTS, or left blank)
|
|
|
|
``hvc<n>``
|
|
Use the hypervisor console device <n>. (This is for both Xen and
|
|
PowerPC hypervisors.)
|
|
- ::
|
|
|
|
console=tty0
|
|
console=ttyS0
|
|
console=hvc0
|
|
|
|
* - ``loglevel``
|
|
- Service VM
|
|
- All kernel messages with a loglevel less than the console loglevel will
|
|
be printed to the console. The loglevel can also be changed with
|
|
``klogd`` or other programs. The loglevels are defined as follows:
|
|
|
|
.. list-table::
|
|
:header-rows: 1
|
|
|
|
* - Loglevel Value
|
|
- Definition
|
|
* - 0 (KERN_EMERG)
|
|
- System is unusable
|
|
* - 1 (KERN_ALERT)
|
|
- Action must be taken immediately
|
|
* - 2 (KERN_CRIT)
|
|
- Critical conditions
|
|
* - 3 (KERN_ERR)
|
|
- Error conditions
|
|
* - 4 (KERN_WARNING)
|
|
- Warning conditions
|
|
* - 5 (KERN_NOTICE)
|
|
- Normal but significant condition
|
|
* - 6 (KERN_INFO)
|
|
- Informational
|
|
* - 7 (KERN_DEBUG)
|
|
- Debug-level messages
|
|
- ::
|
|
|
|
loglevel=7
|
|
|
|
* - ``ignore_loglevel``
|
|
- User VM
|
|
- Ignoring loglevel setting will print **all**
|
|
kernel messages to the console. Useful for debugging.
|
|
We also add it as the ``printk`` module parameter, so users
|
|
can change it dynamically, usually by changing
|
|
``/sys/module/printk/parameters/ignore_loglevel``.
|
|
- ::
|
|
|
|
ignore_loglevel
|
|
|
|
|
|
* - ``log_buf_len``
|
|
- User VM
|
|
- Sets the size of the ``printk`` ring buffer,
|
|
in bytes. n must be a power of two and greater
|
|
than the minimal size. The minimal size is defined
|
|
by the ``LOG_BUF_SHIFT`` kernel config parameter. There is
|
|
also the ``CONFIG_LOG_CPU_MAX_BUF_SHIFT`` config parameter
|
|
that allows to increase the default size depending on
|
|
the number of CPUs. See ``init/Kconfig`` for more details.
|
|
- ::
|
|
|
|
log_buf_len=16M
|
|
|
|
* - ``consoleblank``
|
|
- Service VM, User VM
|
|
- The console blank (screen saver) timeout in
|
|
seconds. Defaults to 600 (10 minutes). A value of 0
|
|
disables the blank timer.
|
|
- ::
|
|
|
|
consoleblank=0
|
|
|
|
* - ``rootwait``
|
|
- Service VM, User VM
|
|
- Wait (indefinitely) for root device to show up.
|
|
Useful for devices that are detected asynchronously
|
|
(e.g., USB and MMC devices).
|
|
- ::
|
|
|
|
rootwait
|
|
|
|
* - ``root``
|
|
- Service VM, User VM
|
|
- Define the root filesystem.
|
|
|
|
``/dev/<disk_name><decimal>``
|
|
represents the device number of the partition - device
|
|
number of disk plus the partition number.
|
|
|
|
``/dev/<disk_name>p<decimal>``
|
|
same as above, this form is used when the disk name of
|
|
the partitioned disk ends with a digit. To separate the
|
|
disk name and partition slot, a ``p`` is inserted.
|
|
|
|
``PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF``
|
|
represents the unique ID of a partition if the
|
|
partition table provides it. The UUID may be either
|
|
an EFI/GPT UUID, or refer to an MSDOS
|
|
partition using the format SSSSSSSS-PP, where SSSSSSSS is a
|
|
zero-filled hexadecimal representation of the 32-bit
|
|
NT disk signature, and PP is a zero-filled hexadecimal
|
|
representation of the 1-based partition number.
|
|
- ::
|
|
|
|
root=/dev/mmcblk0p1
|
|
root=/dev/vda2
|
|
root=PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF
|
|
|
|
* - ``rw``
|
|
- Service VM, User VM
|
|
- Mount the root device read/write on boot.
|
|
- ::
|
|
|
|
rw
|
|
|
|
* - ``tsc``
|
|
- User VM
|
|
- Disable clocksource stability checks for TSC.
|
|
|
|
Format: <string>, where the only supported value is:
|
|
|
|
``reliable``:
|
|
Mark TSC clocksource as reliable, and disable clocksource
|
|
verification at runtime, and the stability checks done at boot.
|
|
Used to enable high-resolution timer mode on older hardware, and in
|
|
virtualized environments.
|
|
- ::
|
|
|
|
tsc=reliable
|
|
|
|
* - ``cma``
|
|
- Service VM
|
|
- Sets the size of the kernel global memory area for
|
|
contiguous memory allocations, and optionally the
|
|
placement constraint by the physical address range of
|
|
memory allocations. A value of 0 disables CMA
|
|
altogether. For more information, see
|
|
``include/linux/dma-contiguous``.
|
|
- ::
|
|
|
|
cma=64M@0
|
|
|
|
* - ``hvlog``
|
|
- Service VM
|
|
- Sets the guest physical address and size of the dedicated hypervisor
|
|
log ring buffer between the hypervisor and Service VM.
|
|
A ``memmap`` parameter is also required to reserve the specified memory
|
|
from the guest VM.
|
|
|
|
If hypervisor relocation is enabled, reserve the memory below 256MB,
|
|
since the hypervisor could be relocated anywhere between 256MB and 4GB.
|
|
|
|
Enable address space layout randomization (ASLR) on the Service VM.
|
|
This ensures that when the guest Linux is relocating the kernel image,
|
|
it will avoid this buffer address.
|
|
|
|
- ::
|
|
|
|
hvlog=2M@0xe00000
|
|
|
|
* - ``memmap``
|
|
- Service VM
|
|
- Mark specific memory as reserved.
|
|
|
|
``memmap=nn[KMG]$ss[KMG]``
|
|
Region of memory to be reserved is from ``ss`` to ``ss+nn``,
|
|
using ``K``, ``M``, and ``G`` representing kilobytes, megabytes, and
|
|
gigabytes, respectively.
|
|
- ::
|
|
|
|
memmap=0x400000$0xa00000
|
|
|
|
* - ``ramoops.mem_address``
|
|
``ramoops.mem_size``
|
|
``ramoops.console_size``
|
|
- Service VM
|
|
- Ramoops is an oops/panic logger that writes its logs to RAM
|
|
before the system crashes. Ramoops uses a predefined memory area
|
|
to store the dump. See `Linux Kernel Ramoops oops/panic logger
|
|
<https://www.kernel.org/doc/html/v4.19/admin-guide/ramoops.html#ramoops-oops-panic-logger>`_
|
|
for details.
|
|
|
|
This buffer should not overlap with hypervisor reserved memory and
|
|
guest kernel image. See ``hvlog``.
|
|
- ::
|
|
|
|
ramoops.mem_address=0xa00000
|
|
ramoops.mem_size=0x400000
|
|
ramoops.console_size=0x200000
|
|
|
|
|
|
* - ``reboot_panic``
|
|
- Service VM
|
|
- Reboot in case of panic.
|
|
|
|
The comma-delimited parameters are:
|
|
|
|
reboot_mode:
|
|
``w`` (warm), ``s`` (soft), ``c`` (cold), or ``g`` (GPIO)
|
|
|
|
reboot_type:
|
|
``b`` (BIOS), ``a`` (ACPI), ``k`` (kbd), ``t`` (triple), ``e`` (EFI),
|
|
or ``p`` (PCI)
|
|
|
|
reboot_cpu:
|
|
``s###`` (SMP, and processor number to be used for rebooting)
|
|
|
|
reboot_force:
|
|
``f`` (force), or not specified.
|
|
- ::
|
|
|
|
reboot_panic=p,w
|
|
|
|
* - ``maxcpus``
|
|
- User VM
|
|
- Maximum number of processors that an SMP kernel
|
|
will bring up during boot.
|
|
|
|
``maxcpus=n`` where n >= 0 limits
|
|
the kernel to bring up ``n`` processors during system boot.
|
|
Giving n=0 is a special case, equivalent to ``nosmp``, which
|
|
also disables the I/O APIC.
|
|
|
|
After booting, you can bring up additional plugged CPUs by executing
|
|
|
|
``echo 1 > /sys/devices/system/cpu/cpuX/online``
|
|
- ::
|
|
|
|
maxcpus=1
|
|
|
|
* - ``nohpet``
|
|
- User VM
|
|
- Don't use the HPET timer.
|
|
- ::
|
|
|
|
nohpet
|
|
|
|
* - ``intel_iommu``
|
|
- User VM
|
|
- Intel IOMMU driver (DMAR) option
|
|
|
|
``on``:
|
|
Enable Intel IOMMU driver.
|
|
|
|
``off``:
|
|
Disable Intel IOMMU driver.
|
|
|
|
``igfx_off``:
|
|
By default, gfx is mapped as a normal device. If a gfx
|
|
device has a dedicated DMAR unit, the DMAR unit is
|
|
bypassed by not enabling DMAR with this option. In
|
|
this case, the gfx device will use the physical address for DMA.
|
|
- ::
|
|
|
|
intel_iommu=off
|
|
|
|
* - ``hugepages``
|
|
``hugepagesz``
|
|
- Service VM, User VM
|
|
- ``hugepages``:
|
|
HugeTLB pages to allocate at boot.
|
|
|
|
``hugepagesz``:
|
|
The size of the HugeTLB pages. On x86-64 and PowerPC,
|
|
this option can be specified multiple times interleaved
|
|
with ``hugepages`` to reserve huge pages of different sizes.
|
|
Valid page sizes on x86-64 are 2M (when the CPU supports Page Size Extension (PSE))
|
|
and 1G (when the CPU supports the ``pdpe1gb`` cpuinfo flag).
|
|
- ::
|
|
|
|
hugepages=10
|
|
hugepagesz=1G
|
|
|
|
* - ``i915.modeset``
|
|
- Service VM
|
|
- GPU driver loading option.
|
|
|
|
``0``:
|
|
Disable the GPU driver loading for Intel GPU device.
|
|
|
|
``1``:
|
|
Enable the GPU driver loading for Intel GPU device.
|
|
- ::
|
|
|
|
i915.modeset=0
|
|
|
|
.. note:: The ``hugepages`` and ``hugepagesz`` parameters are automatically
|
|
taken care of by the ACRN Configurator tool. If users have customized
|
|
hugepage settings to satisfy their particular workloads in the Service VM,
|
|
the ``hugepages`` and ``hugepagesz`` parameters can be redefined in the GRUB
|
|
menu to override the settings from the ACRN Configurator tool.
|