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