[Minios-devel] Some considerations of ARM Unikraft supports

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Simon,

This week I am trying to boot Unikraft on ARM64/KVM platform. In this progress 
I have
got some considerations and written a simple proposal:

My first target is to enable Unikraft on ARM64+Kvm, so this proposal would 
focus on ARM64+Kvm.
But the goal of ARM support is to enable Unikraft on ARM32/ARM64 based 
hypervisors (ARM32/64 Kvm,
ARM64 Xen and etc). So we have to consider to keep current multi-arch framework 
and reuse common
code like virtual drivers for ARM32/ARM64.

1. Modify the folders for multi-architectures
    1.1. Add arm64 folder to unikraft/arch:
             unikraft----arch----arm
                           |-----x86_64
                           |-----arm64 <-- New

         Above folders contains architecture specified Makefile, Config, 
Compiler flags and some
         code. In most cases, these files are exclusive. So we'd better keep 
each arcitecture in
         a standalone floder. This also can avoid doing to much changes to 
Unikraft Makefile.

         If we add arm64 to unikraft/arch/arm, we have to do more ARCH 
comparasion in Makefile:
             unikraft----arch----arm----arm32
                       |      |-----arm64 <-- New
                     |
                       |-----x86_64
         Before:$(UK_BASE)/arch/$(ARCH)/Makefile.uk.
         After:$(UK_BASE)/arch/arm/$(ARCH)/Makefile.uk
         This change is complex, so we'd better to add arm64 folder to 
unikraft/arch.

    1.2. Add arm64 to unikraft/include/uk/arch

    1.3. Add arm64 kvm platform code to unikraft/plat/kvm/arm, and use Makefile 
to select
         objects for correct architecutre:

         ifeq ($(ARCH_X86_64),y)
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/x86/entry64.S
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/x86/cpu_x86_64.c
         else ifeq ($(ARCH_ARM_64),y)
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/arm/entry64.S
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/arm/cpu_arm64.c
         else ifeq ($(ARCH_ARM_64),y)
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/arm/entry.S
            LIBKVMPLAT_SRCS-y += $(LIBKVMPLAT_BASE)/arm/cpu_arm.c
         endif

    1.4. Add a "drivers" folder to unikraft/
         This because we may have some virtual device drivers can be shared 
among platforms.
         For example, we can reuse virtual uart, timer and gic drivers from 
arm32/arm64 Kvm/xen.

2. Bootloader
    2.1. Because of the BIOS, x86 is using multiboot to load kernel on 
Linux-KVM QEMU. But on ARM platforms,
         we can skip the EFI and boot from the Virtual Machine's RAM base 
address. So we can place _libkvmplat_entry
         to the CPU's reset entry by link script. On ARM64 platform, the 
default virtual machine CPU model is cortex A15.

         plat/kvm/arm/link64.ld:
         ENTRY(_libkvmplat_entry)
         SECTIONS {
             . = 0x40000000;

             /* Code */
             _stext = .;

             .text :
             {
                 *(.text)
                 *(.text.*)
             }

             _etext = .;
             ...
         }

    2.2. Use the fixed physical addresses of PL011 uart, timer and GIC. So we 
can skip the device tree parse.
    2.3. Setup exception traps.

3. Support single CPU.

4. Support multiple threads.
    4.1. Implement GIC interrupt controller drivers. If we doesn't specify the 
gic version in QEMU's parameter,
         default GIC will be detected by kvm_arm_vgic_probe. Most ARM hosts are 
using GICv2, GICv3 and GICv4,
         and QEMU will provide GICv2 and GICv3 emulators. For best 
compatibility, we have to implement gicv2
         and gicv3 drivers without MSI/MSI-X support. This means we don't need 
to implement gicv2m, gicv3-its
         for Unikraft in this time.
    4.2. Implment ARMv8 virtual timer driver.

5. Setup a 1:1 mapping pagetable for Physical memory and Virtual memory.
    5.1. Configure MMU
    5.2. Create page tables with 1GB or 2MB block

6. Implement PSCI interface to support machine shutdown.

7. Network, block and etc IO devices?
   Should we have to port virtual device driver like virtio-net, pv-net from 
KVM and Xen?

Regards,
Wei Chen
_______________________________________________
Minios-devel mailing list
Minios-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/minios-devel