503 lines
15 KiB
ReStructuredText
503 lines
15 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 which 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 printk module parameter, so users
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could 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 LOG_BUF_SHIFT kernel config parameter. There is
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also 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 disk name of
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the partitioned disk ends with a digit. To separate
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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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representing 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 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 disables 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:`CONFIG_HV_RAM_START` and :option:`CONFIG_HV_RAM_SIZE`
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does 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 hypervisor could be relocated anywhere between 256MB and 4GB.
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You should enable ASLR on SOS. This ensures that when guest Linux is
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relocating kernel image, 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 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, gfx device will use physical address for DMA.
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- ::
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intel_iommu=off
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Intel GVT-g (AcrnGT) Parameters
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*******************************
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This table gives an overview of all the Intel GVT-g parameters that are
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available to tweak the behavior of the graphics sharing (Intel GVT-g, aka
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AcrnGT) capabilities in ACRN. The `GVT-g-kernel-options`_
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section below has more details on a few select parameters.
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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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* - i915.enable_gvt
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- Service VM
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- Enable Intel GVT-g graphics virtualization support in the host
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- ::
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i915.enable_gvt=1
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* - i915.gvt_workload_priority
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- Service VM
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- Define the priority level of User VM graphics workloads
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- ::
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i915.gvt_workload_priority=1
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* - i915.enable_initial_modeset
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- Service VM
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- On MRB, value must be ``1``. On Intel NUC or UP2 boards, value must be
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``0``. See :ref:`i915-enable-initial-modeset`.
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- ::
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i915.enable_initial_modeset=1
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i915.enable_initial_modeset=0
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* - i915.nuclear_pageflip
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- Service VM,User VM
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- Force enable atomic functionality on platforms that don't have full support yet.
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- ::
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i915.nuclear_pageflip=1
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* - i915.domain_scaler_owner
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- Service VM
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- See `i915.domain_scaler_owner`_
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- ::
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i915.domain_scaler_owner=0x021100
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* - i915.enable_guc
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- Service VM
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- Enable GuC load for HuC load.
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- ::
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i915.enable_guc=0x02
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* - i915.enable_guc
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- User VM
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- Disable GuC
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- ::
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i915.enable_guc=0
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* - i915.enable_hangcheck
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- User VM
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- Disable check GPU activity for detecting hangs.
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- ::
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i915.enable_hangcheck=0
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* - i915.enable_fbc
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- User VM
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- Enable frame buffer compression for power savings
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- ::
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i915.enable_fbc=1
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.. _GVT-g-kernel-options:
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GVT-g (AcrnGT) Kernel Options details
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=====================================
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This section provides additional information and details on the kernel command
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line options that are related to AcrnGT.
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i915.enable_gvt
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---------------
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This option enables support for Intel GVT-g graphics virtualization
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support in the host. By default, it's not enabled, so we need to add
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``i915.enable_gvt=1`` in the Service VM kernel command line. This is a Service
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OS only parameter, and cannot be enabled in the User VM.
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i915.gvt_workload_priority
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--------------------------
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AcrnGT supports **Prioritized Rendering** as described in the
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:ref:`GVT-g-prioritized-rendering` high-level design. This
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configuration option controls the priority level of GVT-g guests.
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Priority levels range from -1023 to 1023.
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The default priority is zero, the same priority as the Service VM. If
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the level is less than zero, the guest's priority will be lower than the
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Service VM, so graphics preemption will work and the prioritized
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rendering feature will be enabled. If the level is greater than zero,
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User VM graphics workloads will preempt most of the Service VM graphics workloads,
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except for display updating related workloads that use a default highest
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priority (1023).
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Currently, all User VMs share the same priority.
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This is a Service VM only parameters, and does
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not work in the User VM.
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.. _i915-enable-initial-modeset:
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i915.enable_initial_modeset
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---------------------------
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At time, kernel graphics must be initialized with a valid display
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configuration with full display pipeline programming in place before the
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user space is initialized and without a fbdev & fb console.
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When ``i915.enable_initial_modeset=1``, the FBDEV of i915 will not be
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initialized, so users would not be able to see the fb console on screen.
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If there is no graphics UI running by default, users will see black
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screens displayed.
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When ``i915.enable_initial_modeset=0`` in Service VM, the plane restriction
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(also known as plane-based domain ownership) feature will be disabled.
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(See the next section and :ref:`plane_restriction` in the ACRN GVT-g
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High Level Design for more information about this feature.)
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In the current configuration, we will set
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``i915.enable_initial_modeset=1`` in Service VM and
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``i915.enable_initial_modeset=0`` in User VM.
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i915.domain_scaler_owner
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========================
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On each Intel GPU display pipeline, there are several plane scalers
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to zoom in/out the planes. For example, if a 720p video is played
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full-screen on a 1080p display monitor, the kernel driver will use a
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scaler to zoom in the video plane to a 1080p image and present it onto a
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display pipeline. (Refer to "Intel Open Source Graphics PRM Vol 7:
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display" for the details.)
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On Broxton platforms, Pipe A and Pipe B each
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have two plane scalers, and Pipe C has one plane scaler. To support the
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plane scaling in AcrnGT guest OS, we introduced the parameter
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``i915.domain_scaler_owner``, to assign a specific scaler to the target
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guest OS.
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As with the parameter ``i915.domain_plane_owners``, each nibble of
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``i915.domain_scaler_owner`` represents the domain id that owns the scaler;
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every nibble (4 bits) represents a scaler and every group of 2 nibbles
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represents a pipe. This is a Service VM only configuration and cannot be
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modified at runtime. Domain ID 0x0 is for the Service VM, the User VM
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use domain IDs from 0x1 to 0xF.
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For example, if we set ``i915.domain_scaler_owner=0x021100``, the Service VM
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owns scaler 1A, 2A; User VM #1 owns scaler 1B, 2B; and User VM #2 owns scaler
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1C.
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i915.enable_hangcheck
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=====================
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This parameter enable detection of a GPU hang. When enabled, the i915
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will start a timer to check if the workload is completed in a specific
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time. If not, i915 will treat it as a GPU hang and trigger a GPU reset.
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In AcrnGT, the workload in Service VM and User VM can be set to different
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priorities. If Service VM is assigned a higher priority than the User VM, the User VM's
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workload might not be able to run on the HW on time. This may lead to
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the guest i915 triggering a hangcheck and lead to a guest GPU reset.
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This reset is unnecessary so we use ``i915.enable_hangcheck=0`` to
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disable this timeout check and prevent guest from triggering unnecessary
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GPU resets.
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