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

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Date:   Thu, 05 Mar 2020 10:51:09 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     anup@...infault.org
CC:     atishp@...shpatra.org, Anup Patel <Anup.Patel@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        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 Tue, 18 Feb 2020 19:28:38 PST (-0800), anup@...infault.org wrote:
> On Wed, Feb 19, 2020 at 12:06 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>>
>> 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.
>
> I have always been in support of having per-hart interrupt controller driver.
>
> I will rebase my RISC-V INTC driver upon latest kernel and send it again.
> Of course, now the situation has changed the RISC-V INTC driver will
> have to consider NOMMU kernel as well.
>
> The last version of RISC-V INTC driver can be found in riscv_intc_v2
> branch of https://github.com/avpatel/linux.git

Thanks.  I think I saw some patches go by, so let's talk over there.

>
>>
>> >> 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.
>
> Sure, no problem.
>
>>
>> >> 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!
>
> Thanks,
> Anup