Re: [PATCH] RISC-V: Place DTB at 3GB boundary instead of 4GB

[Bin Meng <bmeng.cn@gmail.com>]

Hi Atish,

On Sat, Dec 19, 2020 at 3:46 AM Atish Patra <Atish.Patra@wdc.com> wrote:
>
> On Fri, 2020-12-18 at 16:42 +0800, Bin Meng wrote:
> > Hi Atish,
> >
> > On Fri, Dec 18, 2020 at 4:00 PM Atish Patra <Atish.Patra@wdc.com>
> > wrote:
> > >
> > > On Fri, 2020-12-18 at 15:33 +0800, Bin Meng wrote:
> > > > Hi Atish,
> > > >
> > > > On Fri, Dec 18, 2020 at 3:27 PM Atish Patra <Atish.Patra@wdc.com>
> > > > wrote:
> > > > >
> > > > > On Fri, 2020-12-18 at 15:21 +0800, Bin Meng wrote:
> > > > > > Hi Atish,
> > > > > >
> > > > > > On Fri, Dec 18, 2020 at 5:48 AM Atish Patra
> > > > > > <atish.patra@wdc.com>
> > > > > > wrote:
> > > > > > >
> > > > > > > Currently, we place the DTB at 2MB from 4GB or end of DRAM
> > > > > > > which
> > > > > > > ever is
> > > > > > > lesser. However, Linux kernel can address only 1GB of
> > > > > > > memory
> > > > > > > for
> > > > > > > RV32.
> > > > > > > Thus, it can not map anything beyond 3GB (assuming 2GB is
> > > > > > > the
> > > > > > > starting address).
> > > > > > > As a result, it can not process DT and panic if opensbi
> > > > > > > dynamic
> > > > > > > firmware
> > > > > > > is used.
> > > > > > >
> > > > > > > Fix this by placing the DTB at 2MB from 3GB or end of DRAM
> > > > > > > whichever is lower.
> > > > > > >
> > > > > > > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > > > > > > ---
> > > > > > >  hw/riscv/boot.c | 4 ++--
> > > > > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > > > > >
> > > > > >
> > > > > > With this patch, 32-bit sifive_u still does not boot kernel
> > > > > > with
> > > > > > the
> > > > > > following patch applied on 5.10:
> > > > > > https://patchwork.kernel.org/project/linux-riscv/patch/20201217074855.1948743-1-atish.patra@wdc.com/
> > > > > >
> > > > > > Command I used:
> > > > > > $ qemu-system-riscv32 -nographic -M sifive_u -m 1G -smp 5 -
> > > > > > kernel
> > > > > > arch/riscv/boot/Image
> > > > > >
> > > > > > 32-bit virt cannot boot the same kernel image with memory set
> > > > > > to
> > > > > > 2G
> > > > > > either:
> > > > > > $ qemu-system-riscv32 -nographic -M virt -m 2G -smp 4 -kernel
> > > > > > arch/riscv/boot/Image
> > > > > >
> > > > >
> > > > > Hi Bin,
> > > > > As mentioned in the email on the linux mailing list, this patch
> > > > > only
> > > > > solves 2GB problem. sifive_u problem is solved by Alistair's
> > > > > patch[1].
> > > > >
> > > > > He is planning to send the PR soon. The issue with sifive_u
> > > > > boot
> > > > > was it
> > > > > was failing the 32 bit test earlier resulting a 2MB aligned
> > > > > address
> > > > > instead of 4MB.
> > > >
> > > > Ah, I see. However my testing shows that virt with 2G still does
> > > > not
> > > > boot with this patch.
> > > >
> > >
> > > Strange. I verified again with following combination with -bios and
> > > without bios parameter.
> > >
> > > 1. virt 32/64 with 1GB/2GB memory
> > > 2. sifive_u 32/64 bit with 1GB/2GB memory (Alistair's patch
> > > included)
> > >
> > > Can you share the boot log along with the head commit of Qemu and
> > > commandline ? I am using 5.10 kernel with my kernel fix.
> > >
> >
> > I was using Alistair's QEMU repo for testing and 5.10 kernel with
> > your
> > kernel fix:
> >
> > $ git checkout -b testing pull-riscv-to-apply-20201217-1
> > $ apply this patch
> > $ mkdir build;cd build;../configure
> > --target-list=riscv64-softmmu,riscv32-softmmu;make -j
> >
> > $ ./qemu-system-riscv32 -nographic -M virt -m 2G -smp 4 -kernel
> > ~/work/git/linux/arch/riscv/boot/Image
> >
> > OpenSBI v0.8
> >    ____                    _____ ____ _____
> >   / __ \                  / ____|  _ \_   _|
> >  | |  | |_ __   ___ _ __ | (___ | |_) || |
> >  | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
> >  | |__| | |_) |  __/ | | |____) | |_) || |_
> >   \____/| .__/ \___|_| |_|_____/|____/_____|
> >         | |
> >         |_|
> >
> > Platform Name       : riscv-virtio,qemu
> > Platform Features   : timer,mfdeleg
> > Platform HART Count : 4
> > Boot HART ID        : 3
> > Boot HART ISA       : rv32imafdcsu
> > BOOT HART Features  : pmp,scounteren,mcounteren,time
> > BOOT HART PMP Count : 16
> > Firmware Base       : 0x80000000
> > Firmware Size       : 104 KB
> > Runtime SBI Version : 0.2
> >
> > MIDELEG : 0x00000222
> > MEDELEG : 0x0000b109
> > PMP0    : 0x80000000-0x8001ffff (A)
> > PMP1    : 0x00000000-0xffffffff (A,R,W,X)
> > <hangs here>
> >
> > $ ./qemu-system-riscv32 -nographic -M sifive_u -m 2G -smp 5 -kernel
> > ~/work/git/linux/arch/riscv/boot/Image
> >
> > OpenSBI v0.8
> >    ____                    _____ ____ _____
> >   / __ \                  / ____|  _ \_   _|
> >  | |  | |_ __   ___ _ __ | (___ | |_) || |
> >  | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
> >  | |__| | |_) |  __/ | | |____) | |_) || |_
> >   \____/| .__/ \___|_| |_|_____/|____/_____|
> >         | |
> >         |_|
> >
> > Platform Name       : SiFive HiFive Unleashed A00
> > Platform Features   : timer,mfdeleg
> > Platform HART Count : 5
> > Boot HART ID        : 4
> > Boot HART ISA       : rv32imafdcsu
> > BOOT HART Features  : pmp,scounteren,mcounteren
> > BOOT HART PMP Count : 16
> > Firmware Base       : 0x80000000
> > Firmware Size       : 112 KB
> > Runtime SBI Version : 0.2
> >
> > MIDELEG : 0x00000222
> > MEDELEG : 0x0000b109
> > PMP0    : 0x80000000-0x8001ffff (A)
> > PMP1    : 0x00000000-0xffffffff (A,R,W,X)
> > <hangs here>
> >
> > The following is sifive_u with 1G:
> >
> > $ ./qemu-system-riscv32 -nographic -M sifive_u -m 1G -smp 5 -kernel
> > ~/work/git/linux/arch/riscv/boot/Image
> >
> > OpenSBI v0.8
> >    ____                    _____ ____ _____
> >   / __ \                  / ____|  _ \_   _|
> >  | |  | |_ __   ___ _ __ | (___ | |_) || |
> >  | |  | | '_ \ / _ \ '_ \ \___ \|  _ < | |
> >  | |__| | |_) |  __/ | | |____) | |_) || |_
> >   \____/| .__/ \___|_| |_|_____/|____/_____|
> >         | |
> >         |_|
> >
> > Platform Name       : SiFive HiFive Unleashed A00
> > Platform Features   : timer,mfdeleg
> > Platform HART Count : 5
> > Boot HART ID        : 3
> > Boot HART ISA       : rv32imafdcsu
> > BOOT HART Features  : pmp,scounteren,mcounteren
> > BOOT HART PMP Count : 16
> > Firmware Base       : 0x80000000
> > Firmware Size       : 112 KB
> > Runtime SBI Version : 0.2
> >
> > MIDELEG : 0x00000222
> > MEDELEG : 0x0000b109
> > PMP0    : 0x80000000-0x8001ffff (A)
> > PMP1    : 0x00000000-0xffffffff (A,R,W,X)
> > [    0.000000] Linux version 5.10.0-00001-gbf0dad61896d
> > (bmeng@pek-vx-bsp2) (riscv64-linux-gcc (GCC) 8.1.0, GNU ld (GNU
> > Binutils) 2.30) #1 SMP Thu Dec 17 16:48:13 CST 2020
> > [    0.000000] OF: fdt: Ignoring memory range 0x80000000 - 0x80400000
> > [    0.000000] efi: UEFI not found.
> > [    0.000000] Zone ranges:
> > [    0.000000]   Normal   [mem 0x0000000080400000-0x00000000bfffffff]
> > [    0.000000] Movable zone start for each node
> > [    0.000000] Early memory node ranges
> > [    0.000000]   node   0: [mem 0x0000000080400000-
> > 0x00000000bfffffff]
> > [    0.000000] Initmem setup node 0 [mem 0x0000000080400000-
> > 0x00000000bfffffff]
> > [    0.000000] SBI specification v0.2 detected
> > [    0.000000] SBI implementation ID=0x1 Version=0x8
> > [    0.000000] SBI v0.2 TIME extension detected
> > [    0.000000] SBI v0.2 IPI extension detected
> > [    0.000000] SBI v0.2 RFENCE extension detected
> > [    0.000000] SBI v0.2 HSM extension detected
> > [    0.000000] CPU with hartid=0 is not available
> > [    0.000000] CPU with hartid=0 is not available
> >
> > Regards,
> > Bin
>
> May be you forgot to apply this patch for 2GB case on top of Alistair's
> tree? I don't see any issues with exact same setup.

That's really weird. I have:

$ git log --oneline
3ced2fb RISC-V: Place DTB at 3GB boundary instead of 4GB
d31e970 riscv/opentitan: Update the OpenTitan memory layout
3ed2b8a hw/riscv: Use the CPU to determine if 32-bit
094b072 target/riscv: cpu: Set XLEN independently from target
8987cdc4 target/riscv: csr: Remove compile time XLEN checks

I just rebuilt the QEMU binaries but still have the same result. 2G
does not boot on either 'virt' or 'sifive_u'.

$ ./qemu-system-riscv32 -version
QEMU emulator version 5.2.50 (v5.2.0-551-g3ced2fb)
Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers

Maybe it's toolchain related? I am using kernel.org toolchain
riscv64-linux-gcc (GCC) 8.1.0. I see you were using
riscv64-unknown-linux-gnu-gcc (GCC) 10.2.0.

>
> Qemu git log
> ------
> 851966c92cf5 (HEAD) RISC-V: Place DTB at 3GB boundary instead of 4GB
> d31e970a01e7 (tag: pull-riscv-to-apply-20201217-1, alistair/riscv-to-
> apply.next, alistair/riscv-to-apply.for-upstream) riscv/opentitan:
> Update the OpenTitan memory layout
> 3ed2b8ac2dac hw/riscv: Use the CPU to determine if 32-bit
> 094b072c6819 target/riscv: cpu: Set XLEN independently from target
> -------

Regards,
Bin