From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Antony Pavlov <antonynpavlov@gmail.com>,
Rouven Czerwinski <rcz@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH v2 02/11] RISC-V: make RISCV_SBI and RISCV_M_MODE explicitly mutually exclusive
Date: Fri, 7 May 2021 20:08:48 +0200 [thread overview]
Message-ID: <0a6bd853-6f84-b699-a1d1-1b1a18ad50cb@pengutronix.de> (raw)
In-Reply-To: <20210507205249.bff9c677e81494c210205ac4@gmail.com>
Hi,
On 07.05.21 19:52, Antony Pavlov wrote:
> On Fri, 7 May 2021 16:44:24 +0200
> Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>
> Hi Ahmad !
>
>> Hello Antony,
>>
>> On 07.05.21 16:25, Antony Pavlov wrote:
>>>> I would really like to have a riscv{32,64}_defconfig that can just build all boards
>>>> at once. Do you know if this could be dynamically determined?
>>>
>>> At the moment I have not answer.
>>> I'll try to investigate dynamic mode determination, it's very attractive idea.
>>>
>>> On the other hand compile time mode selection is not the show stopper for
>>> "one defconfig to build them all": we have to make STACK_SIZE and MALLOC_SIZE
>>> per-board parameters not per-defconfig parameters like now.
>>>
>>> If we could make STACK_SIZE and MALLOC_SIZE per-board compile-time parameters then
>>> we can make RISC-V mode per-board compile-time parameter too. Is this solution
>>> acceptable?
>>
>> MALLOC_SIZE can be set as 0 and barebox will determine it based on
>> membase + memsize that are set by PBL.
>>
>> STACK_SIZE must be set per Kconfig, but I think even a generous default stack
>> size should accommodate all targets.
>>
>> If we do the same for RISC-V mode that would probably mean having
>> two functions barebox_riscv_machine_entry() and barebox_riscv_supervisor_entry()
>> in PBL that take care to pass the correct info to barebox proper.
>>
>> Apparently, you can determine mode if you catch exceptions:
>> https://forums.sifive.com/t/how-to-determine-the-current-execution-privilege-mode/2823
>
> Hmm, answer is mostly negative:
>
> <<
> RISC-V deliberately doesn’t make it easy for code to discover
> what mode it is running it because this is a virtualisation hole.
> As a general principle, code should be designed for and implicitly
> know what mode it will run in.
>>>
>
>> We don't yet install exception handlers in barebox, but I am fine with using
>> different PBL common code entry functions.
>>
>> What do you think?
>
> I think that adding exception handling to barebox would be very handy.
> At the moment barebox sometimes hangs during my experiments without any error message.
> Even with a simple exception handler that just prints out epc, status and cause registers
> I have much more information on hang reason.
Exception handling would be useful, no doubt. Rouven is looking
into adding that.
I was asking about what you think about adding barebox_riscv_machine_entry()
and barebox_riscv_supervisor_entry(), so PBL entry points can decide for
themselves what mode the rest of barebox should get when riscv_mode() is
called. I'll CC you on the series.
Cheers,
Ahmad
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next prev parent reply other threads:[~2021-05-07 18:09 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-06 22:08 [PATCH v2 00/11] RISC-V: add LiteX SoC support; resurrect nmon Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 01/11] clocksource: timer-riscv: select CSR from device tree Antony Pavlov
2021-05-07 11:34 ` Ahmad Fatoum
2021-05-07 17:41 ` Antony Pavlov
2021-05-07 18:05 ` Ahmad Fatoum
2021-05-06 22:08 ` [PATCH v2 02/11] RISC-V: make RISCV_SBI and RISCV_M_MODE explicitly mutually exclusive Antony Pavlov
2021-05-07 11:42 ` Ahmad Fatoum
2021-05-07 14:25 ` Antony Pavlov
2021-05-07 14:44 ` Ahmad Fatoum
2021-05-07 17:52 ` Antony Pavlov
2021-05-07 18:08 ` Ahmad Fatoum [this message]
2021-05-07 18:36 ` Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 03/11] RISC-V: make it possible to run nmon from PBL C code Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 04/11] RISC-V: boards: erizo: make it possible to use nmon Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 05/11] serial: add litex UART driver Antony Pavlov
2021-05-07 11:45 ` Ahmad Fatoum
2021-05-07 12:02 ` Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 06/11] gpio: add driver for 74xx-ICs with MMIO access Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 07/11] spi: add litex spiflash driver Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 08/11] net: add LiteEth driver Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 09/11] RISC-V: add LiteX SoC and linux-on-litex-vexriscv support Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 10/11] RISC-V: add litex_linux_defconfig Antony Pavlov
2021-05-06 22:08 ` [PATCH v2 11/11] RISC-V: make it possible to build RV32I multi-image with DEBUG_LL=n Antony Pavlov
2021-05-07 10:27 ` Ahmad Fatoum
2021-05-07 10:23 ` [PATCH v2 00/11] RISC-V: add LiteX SoC support; resurrect nmon Ahmad Fatoum
2021-05-07 11:12 ` Antony Pavlov
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