doc: Add tutorial about how to use CAT on UP2
Tracked-On: #2462 Signed-off-by: Tao Yuhong <yuhong.tao@intel.com>
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yuhong.tao@intel.com
David Kinder
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.. _using_cat_up2:
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Using CAT on UP2
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################
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The UP Squared board `(UP2) <https://up-board.org/upsquared/specifications/>`_
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is an x86 maker board based on the Intel Apollo Lake platform and supports
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Cache Allocation Technology (CAT). With this feature, the usage of cache can be
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restricted to each VM. ACRN hypervisor can do that by giving each VM a cache mask,
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so that the VM will not evict the masked cache lines, as shown in :numref:
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`cache-mask-vm`:
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.. figure:: images/using_cat_up2.png
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:align: center
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:name: cache-mask-vm
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Cache usage with Cache Mask
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CAT Support on ACRN
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*******************
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As described at `Intel (R) 64 and IA-32 Architectures Software Developer’s Manual
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<https://software.intel.com/en-us/download/intel-64-and-ia-32-architectures-sdm-combined-volumes-3a-3b-3c-and-3d-system-programming-guide>`_,
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chapter 17.19, volume 3. There are 3 steps to use CAT:
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1. Detect the CAT capability.
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2. Setup cache mask array MSRs, which is referred to as Class of Service (CLOS) array.
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3. Select one of the CLOS array for the CPU, that will be the cache mask of the CPU.
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ACRN integrates the usage of CAT into VM configuration. The CLOS array must be defined
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in the board config source code, and the VM needs to specify which CLOS to use in its VM
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config data. If the platform supports CAT, the CLOS array will be written to the CLOS MSRs
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at CPU init time, and the VM will set CLOS for VCPU at VM launch time.
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The details are shown in :numref:`acrn-cat-hld`:
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.. figure:: images/acrn_cat_hld.png
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:align: center
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:name: acrn-cat-hld
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CAT Support on ACRN
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Tuning CAT in HV debug shell
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############################
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From the ACRN HV debug shell, you can use ``cpuid``, ``wrmsr/rdmsr`` debug commands to
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enumerate CAT capability and tune CAT parameters. You can use the UP2 board's serial port
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for the HV shell (refer to :ref:`getting-started-up2` for setup instructions).
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#. Check CAT ability with ``cupid``. First run ``cpuid 0x10 0x0``, the return value ebx[bit 2]
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reports the L2 CAT is supported. Then run ``cpuid 0x10 0x2`` to query L2 CAT capability,
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the return value eax[bit 4:0] reports the cache mask has 8 bit, and edx[bit 15:0] reports 4 CLOS are
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supported, as shown below:
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.. code-block:: none
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ACRN:\>cpuid 0x10 0x0
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cpuid leaf: 0x10, subleaf: 0x0, 0x0:0x4:0x0:0x0
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ACRN:\>cpuid 0x10 0x2
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cpuid leaf: 0x10, subleaf: 0x2, 0x7:0x0:0x0:0x3
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#. Check PCPU IDs of each VM, the ``vcpu_list`` shows that VM0 is running on PCPU0,
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and VM1 is running on PCPU1:
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.. code-block:: none
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ACRN:\>vcpu_list
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VM ID PCPU ID VCPU ID VCPU ROLE VCPU STATE
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===== ======= ======= ========= ==========
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0 0 0 PRIMARY Running
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1 1 0 PRIMARY Running
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#. Set CLOS with ``wrmsr <reg_num> <value>``, we want VM1 to use the lower 6 ways of cache,
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so CLOS0 is set to 0xc0 for the upper 2 ways, and CLOS1 is set to 0x3f for the lower
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6 ways:
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.. code-block:: none
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ACRN:\>wrmsr -p1 0xd10 0xc0
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ACRN:\>wrmsr -p1 0xd11 0x3f
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#. Attach COS1 to PCPU1. Because MSR IA32_PQR_ASSOC [bit 63:32], we'll write 0x100000000
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to it to use CLOS1
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.. code-block:: none
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ACRN:\>wrmsr –p1 0xc8f 0x100000000
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Configure CAT for VM with VM Configuration
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##########################################
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#. CAT on ACRN can be enabled and configured by modifying source code, so the first
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step is to clone the ACRN source code (if you haven't already):
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.. code-block:: none
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$ git clone https://github.com/projectacrn/acrn-hypervisor.git
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$ cd acrn-hypervisor/
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#. The predefined cache masks can be found at
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``hypervisor/arch/x86/configs/$(CONFIG_BOARD)/board.c``, for UP2 board, that is
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``hypervisor/arch/x86/configs/apl-up2/board.c``, you can change the mask values,
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but note that the CLOS mask must have continuous bits, or a #GP fault can be triggered.
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.. code-block:: none
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:emphasize-lines: 3,7,11,15
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struct platform_clos_info platform_clos_array[4] = {
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{
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.clos_mask = 0xff,
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.msr_index = MSR_IA32_L2_MASK_0,
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},
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{
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.clos_mask = 0xff,
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.msr_index = MSR_IA32_L2_MASK_1,
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},
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{
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.clos_mask = 0xff,
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.msr_index = MSR_IA32_L2_MASK_2,
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},
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{
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.clos_mask = 0xff,
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.msr_index = MSR_IA32_L2_MASK_3,
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},
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};
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#. Set up CLOS in the VM config. If you want a VM to use one of the CLOSs, you need to find its
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configuration data and modify it. We will take SOS on sharing mode as an example. Its
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configuration data can be found at ``hypervisor/arch/x86/configs/vm_config.c``
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.. code-block:: none
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:emphasize-lines: 5,6
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struct acrn_vm_config vm_configs[CONFIG_MAX_VM_NUM] __aligned(PAGE_SIZE) = {
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{
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.type = SOS_VM,
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.name = SOS_VM_CONFIG_NAME,
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.guest_flags = SOS_VM_CONFIG_GUEST_FLAGS | CLOS_REQUIRED,
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.clos = 1,
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.memory = {
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.start_hpa = 0x0UL,
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.size = CONFIG_SOS_RAM_SIZE,
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},
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.os_config = {
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.name = SOS_VM_CONFIG_OS_NAME,
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},
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},
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};
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#. Build the ACRN hypervisor and copy the artifact ``acrn.efi`` to the
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``/boot/EFI/acrn`` directory, see :ref:`getting-started-building` for building instructions.
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.. code-block:: none
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$ make hypervisor BOARD=apl-up2 FIRMWARE=uefi
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...
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# these operations are done on UP2 board
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$ mount /dev/mmcblk0p0 /boot
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$ scp <acrn.efi-at-your-compile-PC> /boot/EFI/acrn
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#. Restart the UP2 board
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