Hi Lukas, On Wed, Sep 5, 2018 at 5:35 PM Auer, Lukas <lukas.a...@aisec.fraunhofer.de> wrote: > > On Wed, 2018-09-05 at 09:28 +0800, Rick Chen wrote: > > > > From: Auer, Lukas [mailto:lukas.a...@aisec.fraunhofer.de] > > > > Sent: Wednesday, September 05, 2018 5:53 AM > > > > To: bmeng...@gmail.com > > > > Cc: Rick Jian-Zhi Chen(陳建志); u-boot@lists.denx.de > > > > Subject: Re: [U-Boot] [PATCH 12/12] riscv: Add QEMU virt board > > support > > > > > > > > On Tue, 2018-09-04 at 17:31 +0800, Bin Meng wrote: > > > > > Hi Lukas, > > > > > > > > > > On Tue, Sep 4, 2018 at 5:39 AM Auer, Lukas > > > > > <lukas.a...@aisec.fraunhofer.de> wrote: > > > > > > > > > > > > On Thu, 2018-08-30 at 00:54 -0700, Bin Meng wrote: > > > > > > > This adds QEMU RISC-V 'virt' board target support, with > > the hope > > > > > > > of helping people easily test U-Boot on RISC-V. > > > > > > > > > > > > > > The QEMU virt machine models a generic RISC-V virtual > > machine > > > > > > > with support for the VirtIO standard networking and block > > > > > > > storage devices. > > > > > > > It has CLINT, PLIC, 16550A UART devices in addition to > > VirtIO > > > > > > > and it also uses device-tree to pass configuration > > information > > > > > > > to guest software. It implements RISC-V privileged > > architecture > > > > > > > spec v1.10. > > > > > > > > > > > > > > Both 32-bit and 64-bit builds are supported. Support is > > pretty > > > > > > > much preliminary, only booting to U-Boot shell with the > > UART > > > > > > > driver on a single core. Booting Linux is not supported > > yet. > > > > > > > > > > > > > > > > > > > For your information and to avoid duplicate work, I am > > working on > > > > > > a patch set that improves RISC-V support in u-boot. I am > > currently > > > > > > able to boot Linux on a multi-core setup in QEMU, but they > > are not > > > > > > quite ready to submit yet. > > > > > > > > > > > > > > > > This is great! My next step is to work on virtio driver > > support in > > > > > U-Boot as qemu-riscv virt machine has these devices but we > > don't > > > > > have corresponding drivers in U-Boot. Then I will try to boot > > Linux > > > > > after that. Good to hear you already boot Linux with qemu- > > riscv! > > > > > Have you already supported virtio drivers in your port? If > > yes, I > > > > > will just hold on and wait for your patch series :-) > > > > > > > > > > > > > Hi Bin, > > > > > > > > Support for the virtio devices would be great! I don't support > > them in > > > > my port, I can only boot a kernel image from RAM. > > > > I only have a driver for the clint0 (core local interrupt > > controller), > > > > which I need for software interrupts to other cores and as a > > timer. > > > > Software interrupts also work over the supervisor binary > > interface > > > > (SBI), which allows u-boot to run in supervisor mode with bbl > > running > > > > in machine mode to handle the SBI calls. > > > > > > > > Hi Bin and Auer > > > > I have already boot bbl run in S-mode and riscv-linux in M-mode via > > u-boot from SD card or FLASH. > > It mean after booting riscv-linux, u-boot will be dead. And no matter > > about kernel. > > Please refer to doc/README.ae350 > > > > May I figure out more clearly what are you going to do ? > > What are you going to do is let u-boot run in S-mode and boot bbl and > > riscv-linux in M-mode, right ? > > It mean after booting bbl and riscv-linux, u-boot will still alive > > and > > handle SBI calls and somethings in S-mode. > > > > Or u-boot is going to replace the role of bbl ? > > > > Rick > > > > Hi Rick, > > Not exactly, my current boot flow is as follows. > > 1. u-boot SPL starts in machine mode and jumps to bbl > 2. bbl starts u-boot proper in supervisor mode > 3. u-boot boots the kernel >
If this is QEMU virt target, there is no need to boot from SPL then U-Boot proper. > bbl is still active once Linux has booted and is used there for its SBI > implementation. Hope this helps. Yes, I am not quite convinced why Linux kernel was designed this way. This is something like x86's SMM or EFI runtime services... Regards, Bin _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
