[U-Boot] [PATCH 4/8] riscv: andes_plic: Fix some wrong configurations

Auer, Lukas lukas.auer at aisec.fraunhofer.de
Thu Nov 14 17:10:09 UTC 2019 

On Thu, 2019-11-14 at 12:57 +0530, Anup Patel wrote:
> On Wed, Nov 13, 2019 at 9:13 AM Rick Chen <rickchen36 at gmail.com> wrote:
> > Hi Lukas
> > 
> > > Hi Rick,
> > > 
> > > On Mon, 2019-11-11 at 15:19 +0800, Rick Chen wrote:
> > > > Hi Lukas
> > > > 
> > > > > Hi Rick,
> > > > > 
> > > > > On Fri, 2019-11-08 at 15:27 +0800, Rick Chen wrote:
> > > > > > Hi Atish
> > > > > > 
> > > > > > > Hi Atish
> > > > > > > 
> > > > > > > > On Thu, 2019-11-07 at 19:41 +0800, Rick Chen wrote:
> > > > > > > > > Hi Anup & Lukas
> > > > > > > > > 
> > > > > > > > > Anup Patel <anup at brainfault.org> 於 2019年11月7日 週四 下午6:44寫道：
> > > > > > > > > > On Thu, Nov 7, 2019 at 3:11 PM Auer, Lukas
> > > > > > > > > > <lukas.auer at aisec.fraunhofer.de> wrote:
> > > > > > > > > > > On Thu, 2019-11-07 at 11:48 +0530, Anup Patel wrote:
> > > > > > > > > > > > On Thu, Nov 7, 2019 at 11:40 AM Rick Chen <rickchen36 at gmail.com
> > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > Hi Anup
> > > > > > > > > > > > > 
> > > > > > > > > > > > > > On Thu, Nov 7, 2019 at 10:45 AM Anup Patel <
> > > > > > > > > > > > > > anup at brainfault.org> wrote:
> > > > > > > > > > > > > > > On Thu, Nov 7, 2019 at 7:04 AM Rick Chen <
> > > > > > > > > > > > > > > rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > > > > Hi Anup
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > On Wed, Nov 6, 2019 at 2:51 PM Rick Chen <
> > > > > > > > > > > > > > > > > rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > Hi Anup
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > On Wed, Nov 6, 2019 at 2:18 PM Anup Patel <
> > > > > > > > > > > > > > > > > > > anup at brainfault.org> wrote:
> > > > > > > > > > > > > > > > > > > > On Wed, Nov 6, 2019 at 12:14 PM Rick Chen <
> > > > > > > > > > > > > > > > > > > > rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > > > > Hi Anup
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > On Tue, Nov 5, 2019 at 7:19 AM Rick Chen <
> > > > > > > > > > > > > > > > > > > > > > rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > > > > > > Hi Anup
> > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > On Thu, Oct 31, 2019 at 1:42 PM Anup
> > > > > > > > > > > > > > > > > > > > > > > > > Patel <anup at brainfault.org> wrote:
> > > > > > > > > > > > > > > > > > > > > > > > > > On Thu, Oct 31, 2019 at 6:30 AM
> > > > > > > > > > > > > > > > > > > > > > > > > > Alan Kao <alankao at andestech.com>
> > > > > > > > > > > > > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Bin,
> > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks for the critics.  Comments
> > > > > > > > > > > > > > > > > > > > > > > > > > > below.
> > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Oct 30, 2019 at
> > > > > > > > > > > > > > > > > > > > > > > > > > > 06:38:00PM +0800, Bin Meng wrote:
> > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Rick,
> > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Oct 30, 2019 at 10:50
> > > > > > > > > > > > > > > > > > > > > > > > > > > > AM Rick Chen <
> > > > > > > > > > > > > > > > > > > > > > > > > > > > rickchen36 at gmail.com> wrote:
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Bin
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hi Rick,
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Oct 25, 2019 at
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 2:18 PM Andes <
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > uboot at andestech.com> wrote:
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > From: Rick Chen <
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > rick at andestech.com>
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > It will work fine due to
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > hart 0 always will be
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > main
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > hart coincidentally. When
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > develop SPL flow, I try
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > force other harts to be
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > main hart. And it will go
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > wrong in sending IPI
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > flow. So fix it.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Fix what? Does this commit
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > contain 2 fixes, or just 1
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > fix?
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > Yes, it include two fixs. But
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > they will cause one negative
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > result
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > that only hart 0 can send ipi
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > to other harts.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Having this fix, any hart
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > can be main hart in U-
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Boot SPL
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > theoretically, but it
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > still fail somewhere.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > After dig in
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > and found there is an
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > assumption that hart 0
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > shall be
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > main hart in OpenSbi.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > So does this mean there is
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > a bug in OpenSBI too?
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > I am not sure if it is a bug.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > Maybe it is a compatible
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > issue.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > There is a limitation that
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > only hart 0 can be main hart
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > in OpenSBI.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > > I don't think OpenSBI has such
> > > > > > > > > > > > > > > > > > > > > > > > > > > > limitation.
> > > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > Please check the source.
> > > > > > > > > > > > > > > > > > > > > > > > > > > https://github.com/riscv/opensbi/blob/master/firmware/fw_base.S#L54
> > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > Apparently, the FIRST TWO LINEs
> > > > > > > > > > > > > > > > > > > > > > > > > > > of the initialization are the
> > > > > > > > > > > > > > > > > > > > > > > > > > > 1. get hart ID.
> > > > > > > > > > > > > > > > > > > > > > > > > > > 2. determine which route to take
> > > > > > > > > > > > > > > > > > > > > > > > > > > based on their ID respectively.
> > > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > > So, I do think OpenSBI has this
> > > > > > > > > > > > > > > > > > > > > > > > > > > signature, if you are not willing
> > > > > > > > > > > > > > > > > > > > > > > > > > > to call it
> > > > > > > > > > > > > > > > > > > > > > > > > > > a limitation.
> > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > This dependency on hart id #0 was
> > > > > > > > > > > > > > > > > > > > > > > > > > not there until we added self-
> > > > > > > > > > > > > > > > > > > > > > > > > > relocation
> > > > > > > > > > > > > > > > > > > > > > > > > > in OpenSBI for FW_DYNAMIC.
> > > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > > I will try to fix this in OpenSBI
> > > > > > > > > > > > > > > > > > > > > > > > > > but we might end-up having
> > > > > > > > > > > > > > > > > > > > > > > > > > boot_lottery.
> > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > I have send a patch to fix this
> > > > > > > > > > > > > > > > > > > > > > > > > OpenSBI:
> > > > > > > > > > > > > > > > > > > > > > > > > "[PATCH] firmware: Introduce
> > > > > > > > > > > > > > > > > > > > > > > > > relocation lottery"
> > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > Can you try above patch and see if
> > > > > > > > > > > > > > > > > > > > > > > > > that helps ?
> > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > > > It will be great if you can provide
> > > > > > > > > > > > > > > > > > > > > > > > > Tested-by to my patch as well.
> > > > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > > I can not find this patch in mailing
> > > > > > > > > > > > > > > > > > > > > > > list.
> > > > > > > > > > > > > > > > > > > > > > > Can you provide a hyperlink ?
> > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > You can try latest riscv/opensbi master.
> > > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > > I have tested the patch on SiFive Unleashed
> > > > > > > > > > > > > > > > > > > > > > multiple times.
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > I have tried this patch, but it fail
> > > > > > > > > > > > > > > > > > > > > firmware: Introduce relocation lottery(
> > > > > > > > > > > > > > > > > > > > > 98f4a208995b027662a7b04a25e4fa5df5f3eefe)
> > > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > > The scenario was as below:
> > > > > > > > > > > > > > > > > > > > > There are 4 harts run in U-Boot SPL, hart 0
> > > > > > > > > > > > > > > > > > > > > play as main hart.
> > > > > > > > > > > > > > > > > > > > > The hart 1 will receive ipi and come into
> > > > > > > > > > > > > > > > > > > > > OpenSBI(0x1000000) from
> > > > > > > > > > > > > > > > > > > > > U-Boot SPL(0x0), meanwhile hart 0,2,3 still
> > > > > > > > > > > > > > > > > > > > > run in U-Boot SPL.
> > > > > > > > > > > > > > > > > > > > > Then hart 1 will do _relocate_copy_to_lower
> > > > > > > > > > > > > > > > > > > > > which will copy data from
> > > > > > > > > > > > > > > > > > > > > 0x1000000 to 0x0.
> > > > > > > > > > > > > > > > > > > > > And it will corrupt U-Boot SPL.
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > The self-relocation in OpenSBI firmwares
> > > > > > > > > > > > > > > > > > > > ensures that OpenSBI firmware
> > > > > > > > > > > > > > > > > > > > are moved to the FW_TEXT_START before entering
> > > > > > > > > > > > > > > > > > > > C code. This helps
> > > > > > > > > > > > > > > > > > > > us load OpenSBI firmwares anywhere in RAM.
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > However, OpenSBI firmwares don't know where the
> > > > > > > > > > > > > > > > > > > > U-Boot SPL is running.
> > > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > > In your case, both OpenSBI FW_DYNAMIC and U-
> > > > > > > > > > > > > > > > > > > > Boot SPL are linked to
> > > > > > > > > > > > > > > > > > > > address same address 0x0. This means secondary
> > > > > > > > > > > > > > > > > > > > HARTs cannot safely
> > > > > > > > > > > > > > > > > > > > wait while primary HART enters OpenSBI. You
> > > > > > > > > > > > > > > > > > > > should hold secondary HARTs
> > > > > > > > > > > > > > > > > > > > in U-Boot SPL only till OpenSBI FW_DYNAMIC and
> > > > > > > > > > > > > > > > > > > > U-Boot proper are
> > > > > > > > > > > > > > > > > > > > loaded in RAM by primary HART. All your HARTs
> > > > > > > > > > > > > > > > > > > > should jump to OpenSBI
> > > > > > > > > > > > > > > > > > > > at the same time after everything is loaded in
> > > > > > > > > > > > > > > > > > > > RAM.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > I see the issue now.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > The U-Boot SPL is first letting secondary HART
> > > > > > > > > > > > > > > > > > > jump to OpenSBI and primary
> > > > > > > > > > > > > > > > > > > HART jumps to OpenSBI at the end.
> > > > > > > > > > > > > > > > > > > (Refer, jump_to_image_no_args() in
> > > > > > > > > > > > > > > > > > > arch/riscv/lib/spl.c)
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > The real issue is FW_TEXT_START being same as U-
> > > > > > > > > > > > > > > > > > > Boot SPL TEXT_START.
> > > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > > If possible please change TEXT base for U-Boot
> > > > > > > > > > > > > > > > > > > SPL or OpenSBI. I think
> > > > > > > > > > > > > > > > > > > changing U-Boot SPL TEXT_START would be
> > > > > > > > > > > > > > > > > > > convenient since this series
> > > > > > > > > > > > > > > > > > > is under review. Thoughts ?
> > > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > Yes.
> > > > > > > > > > > > > > > > > > I know it can avoid corrupting issue with
> > > > > > > > > > > > > > > > > > changing  U-Boot SPL
> > > > > > > > > > > > > > > > > > TEXT_START not equal to OpenSBI TEXT base.
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > I think this issue will be seen on U-Boot SPL running
> > > > > > > > > > > > > > > > > on QEMU as well.
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > > With the following changes, U-Boot SPL text base
> > > > > > > > > > > > > > > > > > can equal to OpenSBI text base
> > > > > > > > > > > > > > > > > > 1 U-Boot pass main hart information (a2) when
> > > > > > > > > > > > > > > > > > jumping to OpenSBI
> > > > > > > > > > > > > > > > > > 2 OpenSBI pick up $a2 to keep playing as main hart,
> > > > > > > > > > > > > > > > > > other harts go to
> > > > > > > > > > > > > > > > > > _wait_relocate_copy_done
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > Overall it's a good suggestion but we cannot use a2
> > > > > > > > > > > > > > > > > register because this
> > > > > > > > > > > > > > > > > will break FW_JUMP and FW_PAYLOAD. Instead, we should
> > > > > > > > > > > > > > > > > pass preferred
> > > > > > > > > > > > > > > > > boot HART id in struct fw_dynamic_info.
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > Sorry, what I want to say shall be a3.
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > I have a patch for this in preferred_boot_hart_v1
> > > > > > > > > > > > > > > > > branch of
> > > > > > > > > > > > > > > > > https://github.com/avpatel/opensbi.git
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > Can you try OpenSBI from above branch ?
> > > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > > You will have to update the "struct fw_dynamic_info"
> > > > > > > > > > > > > > > > > passed to
> > > > > > > > > > > > > > > > > OpenSBI by U-Boot SPL.
> > > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > Main hart will pass struct "fw_dynamic_info" to OpenSBI
> > > > > > > > > > > > > > > > by U-Boot SPL.
> > > > > > > > > > > > > > > > But other harts will NOT pass struct "fw_dynamic_info"
> > > > > > > > > > > > > > > > to OpenSBI by U-Boot SPL.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > That's wrong in U-Boot SPL.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > All HARTs have to follow FW_DYNAMIC protocol and pass
> > > > > > > > > > > > > > > "struct fw_dynamic_info" pointer in 'a2' register.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > So if U-Boot SPL can pass main hart information via a3,
> > > > > > > > > > > > > > > > OpenSBI just
> > > > > > > > > > > > > > > > have the following change
> > > > > > > > > > > > > > > > blt zero, a6, _wait_relocate_copy_done
> > > > > > > > > > > > > > > > change to
> > > > > > > > > > > > > > > > bne a3, a6, _wait_relocate_copy_done
> > > > > > > > > > > > > > > > before this commit
> > > > > > > > > > > > > > > > 98f4a208995b027662a7b04a25e4fa5df5f3eefe
> > > > > > > > > > > > > > > > firmware: Introduce relocation lottery
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > What about FW_JUMP and FW_PAYLOAD? We have no way of
> > > > > > > > > > > > > > > passing
> > > > > > > > > > > > > > > value in a3 for these firmwares because these are not
> > > > > > > > > > > > > > > booted by U-Boot
> > > > > > > > > > > > > > > SPL.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > Also, U-Boot-2019.10 already uses U-Boot SPL support
> > > > > > > > > > > > > > > which does not
> > > > > > > > > > > > > > > pass anything in 'a3' register.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > We should definitely use "struct fw_dynamic_info" for
> > > > > > > > > > > > > > > this so that we can
> > > > > > > > > > > > > > > maintain backward compatibility as well.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > Please make sure that U-Boot SPL passes "struct
> > > > > > > > > > > > > > > fw_dynamic_info"
> > > > > > > > > > > > > > > pointer in 'a2' register for all HARTs.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > > But after this commit 98f4a, main hart become chosen
> > > > > > > > > > > > > > > > from lottery mechanism.
> > > > > > > > > > > > > > > > Maybe I will prefer to change U-Boot SPL text base not
> > > > > > > > > > > > > > > > overlap with
> > > > > > > > > > > > > > > > OpenSBI text start. :)
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > Like I mentioned, we have this issue for U-Boot SPL on
> > > > > > > > > > > > > > > QEMU as well. It's
> > > > > > > > > > > > > > > just that most of us did not notice it for U-Boot SPL on
> > > > > > > > > > > > > > > QEMU.
> > > > > > > > > > > > > > > 
> > > > > > > > > > > > > > > Let's fix this in the right way from start itself.
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > I double checked spl_invoke_opensbi() and it is doing the
> > > > > > > > > > > > > > right thing
> > > > > > > > > > > > > > by passing "struct fw_dyanmic_info" pointer in 'a2'
> > > > > > > > > > > > > > register.
> > > > > > > > > > > > > > (Refer, common/spl/spl_opensbi.c)
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > Not sure, why it is not passing 'a2' register correctly for
> > > > > > > > > > > > > > you ??
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > 
> > > > > > > > > > > > > Yes, you are right. I reply too quickly.
> > > > > > > > > > > > > Other harts will pass struct fw_dyanmic_info in a2 to
> > > > > > > > > > > > > OpenSBI.
> > > > > > > > > > > > > 
> > > > > > > > > > > > > Thanks for your corrections
> > > > > > > > > > > > 
> > > > > > > > > > > > No problem, I am happy to help.
> > > > > > > > > > > > 
> > > > > > > > > > > > BTW, I tried to play around with U-Boot SPL on QEMU.
> > > > > > > > > > > > 
> > > > > > > > > > > > Maybe below changes can help you...
> > > > > > > > > > > 
> > > > > > > > > > > Thanks for looking into this issue! I successfully tested it on
> > > > > > > > > > > QEMU, I
> > > > > > > > > > > had to add a short delay between sending the IPIs to trigger the
> > > > > > > > > > > problem.
> > > > > > > > > > > 
> > > > > > > > > > > We might still run into problems however. Right now, we are
> > > > > > > > > > > assuming
> > > > > > > > > > > that the main hart is the last one to enter OpenSBI. If this is
> > > > > > > > > > > not the
> > > > > > > > > > > case (some delay when handling the IPI), we will have the same
> > > > > > > > > > > problem
> > > > > > > > > > > again. To fix this we could pass the hart mask, containing all
> > > > > > > > > > > harts
> > > > > > > > > > > that have entered U-Boot, to OpenSBI and wait for all harts to be
> > > > > > > > > > > running in OpenSBI. I am not sure how realistic this scenario is,
> > > > > > > > > > > so
> > > > > > > > > > > this might not be needed.
> > > > > > > > > > 
> > > > > > > > > > I agree that we might still run into this issue if primary HART
> > > > > > > > > > enters
> > > > > > > > > > OpenSBI before secondary HARTs. I think this situation can only
> > > > > > > > > > happen on QEMU where each CPU is a thread running on host but
> > > > > > > > > > very unlikely/impossible on real HW.
> > > > > > > > > > 
> > > > > > > > > > Maybe a delay on primary HART in U-Boot SPL after SMP calls to
> > > > > > > > > > secondary HARTs and before jumping to OpenSBI ?
> > > > > > > > > > 
> > > > > > > > > > Regarding hart_mask in fw_dynamic_info, I think the issue will be
> > > > > > > > > > the
> > > > > > > > > > size of the hart_mask. It is possible in-future SOC vendors come-up
> > > > > > > > > > with SOC having huge number of HARTs OR SOC with discontinuous
> > > > > > > > > > HART IDs which can cause a 64bit hart_mask to be not sufficient for
> > > > > > > > > > all HARTs.
> > > > > > > > > > 
> > > > > > > > > > Also, waiting for all HARTs to enter OpenSBI will be one more wait-
> > > > > > > > > > loop
> > > > > > > > > > in fw_base.S which will add to the boot-time as well.
> > > > > > > > > > 
> > > > > > > > > > I still think the root cause of the issue is that TEXT_START of
> > > > > > > > > > U-Boot SPL and OpenSBI FW_DYNAMIC is same. Maybe we can
> > > > > > > > > > insist SOC vendors to not use same TEXT_START ?
> > > > > > > > > 
> > > > > > > > > I have try your changes about boot_hart for U-Boot SPL with OpenSBI,
> > > > > > > > > preferred_boot_hart_v2 branch
> > > > > > > > > It still encounter some booting problems. I try to find out the root
> > > > > > > > > cause but in vain.
> > > > > > > > > 
> > > > > > > > 
> > > > > > > > Just wanted to make sure that you have tried this patch.
> > > > > > > > 
> > > > > > > > http://lists.infradead.org/pipermail/opensbi/2019-November/000672.html
> > > > > > > > 
> > > > > > > > We should investigate the issue why it did not work for you if this
> > > > > > > > patch did not work for you.
> > > > > > > 
> > > > > > > Yes, I try with this
> > > > > > > commit 831aa3c1ad2546a2b35ddf5b1aa0ce91cdc7fe89
> > > > > > > firmware: Add preferred boot HART field in struct fw_dynamic_info
> > > > > > > 
> > > > > > > It fail randomly yesterday, but this morning I try several times it will pass.
> > > > > > > I will keep trying.
> > > > > > > 
> > > > > > 
> > > > > > I have figure out one fail case which is belong to main hart of U-Boot
> > > > > > SPL is not the last hart while entering OpenSBI
> > > > > > 
> > > > > 
> > > > > Can you try this branch [1]? It includes a quick implementation of the
> > > > > changes a mentioned yesterday, where the main hart waits until all
> > > > > harts have received the IPI.
> > > > > 
> > > > > [1]:
> > > > > https://github.com/lukasauer/u-boot/commits/riscv-opensbi-boot-hart
> > > > 
> > > > I have try this patch, but it seems can not guarantee main hart to be
> > > > the last hart while leaving U-Boot SPL.
> > > > Even the main hart have checked all harts have received the IPI, but
> > > > it still have opportunities to arrive OpenSBI  before other harts.
> > > > 
> > > 
> > > Thanks for testing! Can you try again with the same branch? I added
> > > another patch so that clearing the IPI is the very last thing before
> > > jumping to the SMP function.
> > > If that does not help, we'll have to add a delay in
> > > spl_invoke_opensbi() to delay the main hart.
> > 
> > Thanks for your patch, it indeed solve the problem almost.
> > It always pass the booting verification under free running, I try many
> > times and can not hit the failure case.
> > 

Thanks for testing the changes again, Rick. I will try to clean them up
and submit them soon.

> > But if I do something with GDB, E.g
> > Set a break in 0x6c2 (c.jalr  s2) in handle_ipi() and then delete the
> > break and free run after it hit this break
> > then it will hit the failure case as below:
> 
> The current booting mechanism where all HARTs jump to each
> booting stage (including Linux) at the same time is very fragile.
> 
> Attaching a debugger at boot-time will certainly break current way
> of booting all HARTs because we are holding a particular HART in
> debug state. I am not sure if we can handle the debugger case in
> software but in real-world deployments debugger won't be present
> so maybe we can ignore this case.
> 
> The SBI v0.2 HSM extension will make things better. It would be
> even better if HW designers provide explicit HW mechanism to
> power-on/off HARTs at run-time.
> 

I agree with you, Anup. The debugger should not be attached in real-
world scenarios. Even if it is, it is likely for debugging something in
U-Boot proper or SPL and not the part where we are jumping to OpenSBI,
so we should not typically run into any issues here. In addition, the
recommended way of using SPL should be with separate text bases for  
U-Boot SPL and OpenSBI. In this setup we don't run into this problem.
All in all, I think the current solution is robust enough.

I will also make sure to add a comment on why it is important that the
main hart enters OpenSBI last. This way the problem is documented and
people looking at the code will be aware of it.

Thanks,
Lukas

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