From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: Re: powerpc/powernv: call OPAL_QUIESCE before OPAL_SIGNAL_SYSTEM_RESET
Date: Tue, 5 Jun 2018 00:10:51 +1000 (AEST) [thread overview]
Message-ID: <40zxg04Z4wz9s5R@ozlabs.org> (raw)
In-Reply-To: <20180510122148.3996-1-npiggin@gmail.com>
On Thu, 2018-05-10 at 12:21:48 UTC, Nicholas Piggin wrote:
> Although it is often possible to recover a CPU that was interrupted
> from OPAL with a system reset NMI, it's undesirable to interrupt them
> for a few reasons. Firstly because dump/debug code itself needs to
> call firmware, so it could hang on a lock or possibly corrupt a
> per-cpu data structure if it or another CPU was interrupted from
> OPAL. Secondly, the kexec crash dump code will not return from
> interrupt to unwind the OPAL call.
>
> Call OPAL_QUIESCE with QUIESCE_HOLD before sending an NMI IPI to
> another CPU, which wait for it to leave firmware (or time out) to
> avoid this problem in normal conditions. Firmware bugs may still
> result in a timeout and interrupting OPAL, but that is the best
> option (stops the CPU, and possibly allows firmware to be debugged).
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/ee03b9b4479d1302d01cebedda3518
cheers
prev parent reply other threads:[~2018-06-04 14:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-10 12:21 [PATCH] powerpc/powernv: call OPAL_QUIESCE before OPAL_SIGNAL_SYSTEM_RESET Nicholas Piggin
2018-06-04 14:10 ` Michael Ellerman [this message]
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