linux-kernel - Re: [PATCH] RISC-V: Don't enable all interrupts in trap

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Message-ID: <mhng-afe8915b-f34a-49e5-86fd-92f5de4100ed@palmerdabbelt-glaptop1>
Date:   Tue, 18 Feb 2020 10:36:27 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     atishp@...shpatra.org
CC:     Anup Patel <Anup.Patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Damien Le Moal <Damien.LeMoal@....com>, anup@...infault.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Atish Patra <Atish.Patra@....com>,
        Alistair Francis <Alistair.Francis@....com>,
        linux-riscv@...ts.infradead.org, Christoph Hellwig <hch@....de>
Subject:     Re: [PATCH] RISC-V: Don't enable all interrupts in trap_init()

On Sun, 02 Feb 2020 03:48:18 PST (-0800), atishp@...shpatra.org wrote:
> On Sun, Feb 2, 2020 at 3:06 AM Anup Patel <anup.patel@....com> wrote:
>>
>> Historically, we have been enabling all interrupts for each
>> HART in trap_init(). Ideally, we should only enable M-mode
>> interrupts for M-mode kernel and S-mode interrupts for S-mode
>> kernel in trap_init().
>>
>> Currently, we get suprious S-mode interrupts on Kendryte K210
>> board running M-mode NO-MMU kernel because we are enabling all
>> interrupts in trap_init(). To fix this, we only enable software
>> and external interrupt in trap_init(). In future, trap_init()
>> will only enable software interrupt and PLIC driver will enable
>> external interrupt using CPU notifiers.

I think we should add a proper interrupt controller driver for the per-hart
interrupt controllers, as doing this within the other drivers is ugly -- for
example, there's no reason an MMIO timer or interrupt controller driver should
be toggling these bits.

>> Cc: stable@...r.kernel.org
>> Fixes: 76d2a0493a17 ("RISC-V: Init and Halt Code)

I'd argue this actually fixes the M-mode stuff, since that's the first place
this issue shows up.  I've queued this with

Fixes: a4c3733d32a7 ("riscv: abstract out CSR names for supervisor vs machine mode")

instead, as that's the first commit that will actually write to MIE and
therefor the first commit that will actually exhibit bad behavior.  It also has
the advantage of making the patch apply on older trees, which should make life
easier for the stable folks.

>> Signed-off-by: Anup Patel <anup.patel@....com>
>> ---
>>  arch/riscv/kernel/traps.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
>> index f4cad5163bf2..ffb3d94bf0cc 100644
>> --- a/arch/riscv/kernel/traps.c
>> +++ b/arch/riscv/kernel/traps.c
>> @@ -156,6 +156,6 @@ void __init trap_init(void)
>>         csr_write(CSR_SCRATCH, 0);
>>         /* Set the exception vector address */
>>         csr_write(CSR_TVEC, &handle_exception);
>> -       /* Enable all interrupts */
>> -       csr_write(CSR_IE, -1);
>> +       /* Enable interrupts */
>> +       csr_write(CSR_IE, IE_SIE | IE_EIE);
>>  }
>> --
>> 2.17.1
>>
>>
>
> Looks good.
> Reviewed-by: Atish Patra <atish.patra@....com>

Tested-by: Palmer Dabbelt <palmerdabbelt@...gle.com> [QMEU virt machine with SMP]
Reviewed-by: Palmer Dabbelt <palmerdabbelt@...gle.com>

I consider this a bugfix, so I'm targeting it for RCs.  It's on fixes and
should go up this week.

Thanks!