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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Minios-devel] Some considerations of ARM Unikraft supports
Hi Simon, > -----Original Message----- > From: Simon Kuenzer [mailto:simon.kuenzer@xxxxxxxxx] > Sent: 2018年2月7日 0:34 > To: Wei Chen <Wei.Chen@xxxxxxx>; Julien Grall <julien.grall@xxxxxxxxxx> > Cc: Felipe Huici <Felipe.Huici@xxxxxxxxx>; Kaly Xin <Kaly.Xin@xxxxxxx>; Shijie > Huang <Shijie.Huang@xxxxxxx>; Florian Schmidt <Florian.Schmidt@xxxxxxxxx>; > Costin Lupu <costin.lup@xxxxxxxxx>; nd <nd@xxxxxxx>; minios- > devel@xxxxxxxxxxxxx > Subject: Re: [Minios-devel] Some considerations of ARM Unikraft supports > > Hi Wei, > > On 06.02.2018 08:58, Wei Chen wrote: > > Hi Simon, > > > >> -----Original Message----- > >> From: Simon Kuenzer [mailto:simon.kuenzer@xxxxxxxxx] > >> Sent: 2018年2月6日 0:21 > >> To: Wei Chen <Wei.Chen@xxxxxxx>; Julien Grall <julien.grall@xxxxxxxxxx> > >> Cc: Felipe Huici <Felipe.Huici@xxxxxxxxx>; Kaly Xin <Kaly.Xin@xxxxxxx>; > Shijie > >> Huang <Shijie.Huang@xxxxxxx>; Florian Schmidt <Florian.Schmidt@xxxxxxxxx>; > >> Costin Lupu <costin.lup@xxxxxxxxx>; nd <nd@xxxxxxx>; minios- > >> devel@xxxxxxxxxxxxx > >> Subject: Re: [Minios-devel] Some considerations of ARM Unikraft supports > >> > >> Hi Wei, hi Julien, > >> > >> thanks a lot for discussing this already, I put my comments inline. > >> > >> On 05.02.2018 08:22, Wei Chen wrote: > >>> Hi Julien, > >>> > >>> Thanks for your comments! > >>> Replies inline. > >>> > >>>> -----Original Message----- > >>>> From: Julien Grall [mailto:julien.grall@xxxxxxxxxx] > >>>> Sent: 2018年2月2日 18:43 > >>>> To: Wei Chen <Wei.Chen@xxxxxxx>; Simon Kuenzer <simon.kuenzer@xxxxxxxxx> > >>>> Cc: Felipe Huici <Felipe.Huici@xxxxxxxxx>; Kaly Xin <Kaly.Xin@xxxxxxx>; > >> Shijie > >>>> Huang <Shijie.Huang@xxxxxxx>; Florian Schmidt > >>>> <Florian.Schmidt@xxxxxxxxx>; > >>>> Costin Lupu <costin.lup@xxxxxxxxx>; nd <nd@xxxxxxx>; minios- > >>>> devel@xxxxxxxxxxxxx > >>>> Subject: Re: [Minios-devel] Some considerations of ARM Unikraft supports > >>>> > >>>> Hi, > >>>> > >>>> On 02/02/18 09:10, Wei Chen wrote: > >>>>> 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. > >>>> > >>>> Except the assembly code, most of the C code should be very similar > >>>> between ARM64 and ARM32. So it might make more sense to have a directory > >>>> arch/arm with sub-folder arm32 and arm64. > >>>> > >>> > >>> This is one option I had considered. But this will add a new variable > >> (VENDOR) to > >>> make scripts. e.g. :$(UK_BASE)/arch/$(VENDOR)/$(ARCH)/Makefile.uk > >>> And currently, only architecture dependent code will be placed in $(ARCH) > >> folder. > >>> For example, in arm folder, there are some files for arm32 math library. > >> These > >>> files can only be used for arm32. > >> > >> What is this vendor variable about? Is it something that applies to a > >> specific silicon? Is it required to add subfolders for it? > >> > > > > Yes, it applies to a specific silicon. But "VENDOR" is not very accurate > here. > > I had considered it again, because x86 is not a "VENDOR", and not all x86 > chips > > Belong to intel, Maybe use "FAMILY" is better. > > > > If we really have some common C code for ARM32/64, I agree to add subfolders > > for it. > > > > unikraft----arch----arm----arm32 ARM family arm32 and arm64 architectures > > | |-----arm64 > > | > > |------x86----i386 > > |-----x86_64 X86 family i386 and x86_64 architectures > > > > Sorry, I forgot to mention that you also should add only code here which: > 1) ...is exposed to the user with an interface in include/uk/arch/* > 2) ...works with all platforms (including linuxu which is special). > So for instance, you should not add code that uses privileged > instruction that could not be executed in Linux userspace. If there > is a different implementation needed, it is a hint that this > functionality need to be moved to the platform API > (include/uk/plat/*) > Ahh, I understand now. Thanks for your explanation. > I had a discussion with Costin, and we were thinking of placing code > that is shared by multiple platforms (but not by all, or is not > architecture code) in plat/common/arm/* and plat/common/arm/arm64/*. > Your platforms libs would include the source files from this directory. > > Subdirectories (for e.g., timer, GIC) are fine. What do you think? If > you agree we will put a commit that introduces a structure to the > staging branch. > I think this idea is good. But the example here is not very accurate ; ) Once the "drivers" folder has been introduced, I still want to move the timer, GIC to it. > >>> > >>> If some C codes are very similar between arm32 and arm64, I think this > code > >> would > >>> be very similar between arm and x86 too. We can place these codes in > >> Unikraft/lib. > >>> > >>> Above 2 options would affect the common framework, so I still want to get > >> some > >>> Comments from Simon. > >> > >> I welcome this discussion because one of the exercises of Unikraft's 0.2 > >> releases is to figure out how to do the right split. > >> I am okay with changing the structure of the arch folder substructure if > >> we can foresee already that it will make sense. In such a case, I would > >> also like to adopt the same principle to the x86 architecture folder. > >> > >> The idea of architecture libraries is that they contain code which is > >> only special to the CPU but the same to all of the target platforms > >> (xen, kvm, linux). We were originally expecting that this is mostly > >> assembly code but we might be wrong with our original assumption. So, if > >> you foresee any common C code for 32 and 64bit ARM that would be > >> duplicated otherwise, we should use a single arm folder instead. > >> > > > > Sorry, about " use a single arm folder instead". Does it mean we don't add > > Any subfolders to arm or x86 folder? Like following? > > > > unikraft----arch----arm > > | > > |------x86 > > > > Sorry, I wasn't clear. I meant: > arch/arm/* > > with specific code in: > > arch/arm/arm32 > arch/arm/arm64 > Thanks for your clarification, I got it now. > >>> > >>>>> > >>>>> 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. > >> > >> Is it okay for you to wait with the driver folder a bit? I am currently > >> working on PCI for x86 KVM and I figured that Unikraft need an mechanism > >> to select drivers for devices (and maybe buses) individually for each > >> platform. But drivers are still something that depend on the platform. > >> For instance Xen could reuse the same PCI drivers with pcifront, linux > >> with VFIO, but a third platform might not support PCI at all. > >> > >> Because of this, I am currently considering to introduce an folder in > >> plat: e.g., plat/common/drivers/pci/virtio-net. What do you guys think? > >> > > > > That's quite good, I will wait it : ) > > > >>>>> > >>>>> 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. > >>>> > >>>> Cortex A15 does not support 64-bit. So how come it is the default > >>>> virtual machine CPU model for ARM64? > >>>> > >>> > >>> From the code, if we don't specify any cpumodel, the mach-virt's default > >>> cpumodel will be set to "cortex-a15". But you'are right, if we use cortex- > 15 > >>> by default, we can run any 64-bit image. Here is my mistake. We have to > set > >>> correct cpumodel (cortex-a53/a57 or host) in command line to make 64-bit > >> image > >>> work. But the mach-virt is still using the a15memmap and a15irqmap. > >>> > >>> > >>>> But likely, you want to expose the same MIDR as the underlying CPU. So > >>>> if an errata has to be implemented in Unikraft, it will be able to know > it. > >>>> > >>> > >>> Exposing the underlying CPU's MIDR to guest is depending on the > hypervisors. > >>> For Unikraft itself, it doesn't know whether this MIDR is the same as the > >> underlying > >>> CPU or not. And actually, no matter what cpumodel the hypervisor is > >> emulating, the > >>> code is running on the physical CPU directly. We don't emulate the CPU > >> instructions. > >>> If we run Unikraft on a corext-a53 host CPU, we can compile this image > with > >> gcc flags > >>> like fix-a53-error. > >>> > >>>>> > >>>>> 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. > >>>> > >>>> What does promise you the PL011, timer, GIC will always be at the same > >>>> address? > >>> > >>> My original idea was that we selected a fixed machine (mach-virt) for > >> Unikraft to run. > >>> In this case, the memory map is fixed. > >>> > >>>> Or do you expect the user to hack unikraft build system to set > >>>> the address? > >>>> > >>> > >>> For my opinion, Yes. Why should we need to parse the device tree to > increase > >> our boot > >>> time and footprint? > >>> > >> > >> Sorry for my stupid question: Would this hardcode the guest device > >> configuration that you would need to set with KVM? I mean, how are > >> network devices (or other) are handover to the guest? If yes, I am > >> concerned that Unikraft is getting difficult to use on ARM. I would > >> rather prefer to provide a configuration option where users could > >> disable that the image scans the device tree and expects devices at > >> hardcoded places. > > > > While I was writing this proposal, I hadn't consider so many devices. I just > > considered some platform devices like interrupt controller, timer and UART. > > At that moment, I prefer to hardcode. But now I think parse the device tree > > is better. Because the virtual net/block devices are dynamic configuration > > for a VM. > > > > Good. Unikraft has libfdt already included. You probably should use this > one for doing the parsing and depend the platform libraries on it (see > arm32 platforms). > > >> > >>>> At least from Xen PoV, the memory layout is not part of the ABI and a > >>>> guest should rely on the DT for getting the correct addresses. > >>>> > >>> > >>> I understand your concern. It's not a part of the ABI. So the addresses > can > >> be changed > >>> for different boards. > >>> > >>> I think we must do a tradeoff between flexibility and deploy density (boot > >> time and footprint) > >>> > >> > >> If this makes sense for you: I prefer having the most flexible as > >> default and provide configuration options with Config.uk to switch them > >> off individually. I think Unikraft should handover such tradeoff > >> question to Unikernel builders. > >> > > > > That would be good. > > > > Perfect ;-) > > >>>>> 2.3. Setup exception traps. > >>>>> > >>>>> 3. Support single CPU. > >> > >> This is fine for the first version. The other platforms also just > >> support a single CPU for now. > >> > >>>>> > >>>>> 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. > >>>>> > >> > >> Please contact Costin what is required from the Unikraft's scheduler > >> API. I CC'ed him. > >> > > > > Thanks, I will contact Costin when I start to implement this 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 > >>>>> > >> > >> Good. > >> > >>>>> 6. Implement PSCI interface to support machine shutdown. > >>>> > >>>> FWIW, system_off only exist from PSCI 0.2 and onwards. > >>>> > >>> > >>> It seem the psci-0.2 is the default PSCI version of mach-virt with KVM. > >>> > >>>>> > >>>>> 7. Network, block and etc IO devices? > >>>>> Should we have to port virtual device driver like virtio-net, pv- > net > >>>> from KVM and Xen? > >> > >> After we agreed how Unikraft should include drivers we can start with > >> porting them. Is KVM on ARM using virtio-net, too? Is there a virtual > >> PCI bus attached? > > > > Yes, KVM on ARM is using virtio-net too. The virtio-net is connect to a > > virtio-mmio bus. But there is a ECAM PCI host controller emulator too. > > > > How are other devices attached? For instance block devices. I remember > we have SD card emulation. Maybe we need another bus driver that uses > FDT later to make them work in Unikraft. > By default, all virtio devices will attach to virtio-mmio bus. PCI Pass through devices can be connected to ECAM PCI host emulate. So if we want to support ARM PCI pass through, we have to implement ECAM PCI host driver for Unikraft. If you want to add a SD Card controller to VM. This controller may attach to Platform bus or simple-bus. SD_MMC_1@B000000 { ===>> attach SD MMC to platform bus compatible = "SD1..."; } platform@c000000 { compatible = "qemu,platform", "simple-bus"; ranges = <0x0 0x0 0xc000000 0x2000000>; interrupt-parent = <0x8001>; #address-cells = <0x1>; #size-cells = <0x1>; SD_MMC_2@c003000 { ===>> attach SD MMC to simple bus compatible = "SD2..."; } }; Both of above buses are very simple. We should implement them for Unikraft. But I am not sure what is the "SD card emulation" meaning? Is it a SD card Controller emulator for guest or just a block device? If it's a block device, Why should we have to care about is it a SD card or not? > >> > >>>> > >>>> There are no emulation provided on Xen, so you would need PV drivers to > >>>> get access to the network/block. > >> > >> This is fine ;-). > >> > >>> > >>> Yes, I have the same opinion with you 😊 > >>> > >>> > >>>> > >>>> Cheers, > >>>> > >>>> -- > >>>> Julien Grall > >> > >> Thanks, > >> > >> Simon > > Thanks, > > Simon _______________________________________________ Minios-devel mailing list Minios-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/minios-devel
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