148 lines
4.8 KiB
ReStructuredText
148 lines
4.8 KiB
ReStructuredText
.. _faq:
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FAQ
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###
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Here are some frequently asked questions about the ACRN project.
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.. contents::
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:local:
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:backlinks: entry
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------
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What hardware does ACRN support?
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********************************
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ACRN runs on Intel Apollo Lake and Kaby Lake boards, as documented in
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our :ref:`hardware` documentation.
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Clear Linux* OS fails to boot on my NUC
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***************************************
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If you're following the :ref:`getting_started` documentation and the NUC
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fails to boot, here are some options to try:
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* Upgrade your platform to the latest BIOS
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* Verify Secure Boot is disabled in the BIOS settings:
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- Depending on your platform, press for example, :kbd:`F2` while
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booting to enter the BIOS options menu, and verify "Secure Boot" is
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not checked in the "Boot Options"
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* Make sure you are using EFI (and not legacy BIOS)
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How do I configure ACRN's memory use?
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*************************************
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It's important that the ACRN Kconfig settings are aligned with the physical memory
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on your platform. Check the documentation for these option settings for
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details:
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* :option:`CONFIG_PLATFORM_RAM_SIZE`
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* :option:`CONFIG_SOS_RAM_SIZE`
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* :option:`CONFIG_UOS_RAM_SIZE`
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* :option:`CONFIG_HV_RAM_SIZE`
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For example, if memory is 32G, setup ``PLATFORM_RAM_SIZE`` = 32G
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::
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config PLATFORM_RAM_SIZE
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hex "Size of the physical platform RAM"
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default 0x200000000 if PLATFORM_SBL
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default 0x800000000 if PLATFORM_UEFI
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Setup ``SOS_RAM_SIZE`` = 32G too (The SOS will have the whole resource)
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::
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config SOS_RAM_SIZE
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hex "Size of the Service OS (SOS) RAM"
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default 0x200000000 if PLATFORM_SBL
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default 0x800000000 if PLATFORM_UEFI
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Setup ``UOS_RAM_SIZE`` to what you need, for example, 16G
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::
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config UOS_RAM_SIZE
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hex "Size of the User OS (UOS) RAM"
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default 0x100000000 if PLATFORM_SBL
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default 0x400000000 if PLATFORM_UEFI
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Setup ``HV_RAM_SIZE`` (we will reserve memory for guest EPT paging
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table), if you setup 32G (default 16G), you must enlarge it with
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(32G-16G)/2M pages (where pages are 4K). The example below is after
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HV_RAM_SIZE is changed to 240M
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::
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config HV_RAM_SIZE
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hex "Size of the RAM region used by the hypervisor"
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default 0x07800000 if PLATFORM_SBL
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default 0x0f000000 if PLATFORM_UEFI
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How to modify the default display output for a UOS?
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***************************************************
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Apollo Lake HW has three pipes and each pipe can have three or four planes which
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help to display the overlay video. The hardware can support up to 3 monitors
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simultaneously. Some parameters are available to control how display monitors
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are assigned between the SOS and UOS(s), simplifying the assignment policy and
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providing configuration flexibility for the pipes and planes for various IoT
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scenarios. This is known as the **plane restriction** feature.
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* ``i915.avail_planes_per_pipe``: for controlling how planes are assigned to the
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pipes
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* ``i915.domain_plane_owners``: for controlling which domain (VM) will have
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access to which plane
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Refer to :ref:`GVT-g-kernel-options` for detailed parameter descriptions.
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In the default configuration, pipe A is assigned to the SOS and pipes B and C
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are assigned to the UOS, as described by these parameters:
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* SOS::
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i915.avail_planes_per_pipe=0x01010F
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i915.domain_plane_owners=0x011111110000
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* UOS::
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i915.avail_planes_per_pipe=0x0070F00
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To assign pipes A and B to the UOS, while pipe C is assigned to the SOS, use
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these parameters:
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* SOS::
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i915.avail_planes_per_pipe=0x070101
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i915.domain_plane_owners=0x000011111111
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* UOS::
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i915.avail_planes_per_pipe=0x000F0F
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.. note::
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The careful reader may have noticed that in all examples given above, the SOS
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always has at least one plane per pipe. This is intentional, and the driver
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will enforce this if the parameters do not do this.
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Why does ACRN need to know how much RAM the system has?
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*******************************************************
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Configuring ACRN at compile time with the system RAM size is a tradeoff between
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flexibility and functional safety certification. For server virtualization, one
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binary is typically used for all platforms with flexible configuration options
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given at run time. But, for IoT applications, the image is typically configured
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and built for a particular product platform and optimized for that product.
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Important features for ACRN include Functional Safety (FuSa) and real-time
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behavior. FuSa requires a static allocation policy to avoid the potential of
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dynamic allocation failures. Real-time applications similarly benefit from
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static memory allocation. This is why ACRN removed all ``malloc()``-type code,
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and why it needs to pre-identify the size of all buffers and structures used in
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the Virtual Memory Manager. For this reason, knowing the available RAM size at
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compile time is necessary to statically allocate memory usage.
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