linux-kernel - Re: [PATCH 1/1] arm64: kexec: machine_kexec should call __flush_icache_range

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Date:   Mon, 30 Jul 2018 11:46:24 -0500
From:   Dave Kleikamp <dave.kleikamp@...cle.com>
To:     Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] arm64: kexec: machine_kexec should call
 __flush_icache_range

On 07/30/2018 11:22 AM, Will Deacon wrote:
> On Mon, Jul 30, 2018 at 05:16:42PM +0100, Catalin Marinas wrote:
>> On Mon, Jul 30, 2018 at 10:29:21AM -0500, Dave Kleikamp wrote:
>>> machine_kexec flushes the reboot_code_buffer from the icache
>>> after stopping the other cpus.
>>>
>>> Commit 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache
>>> for kernel mappings") added an IPI call to flush_icache_range, which
>>> causes a hang here, so replace the call with __flush_icache_range
>>
>> While machine_kexec() may be called with interrupts disabled (IIUC) and
>> we shouldn't IPI other CPUs, I don't understand why it hangs here. Are
>> there any other CPUs online at this point?
> 
> The BUG_ON and WARN_ON at the start of machine_kexec() suggest to me that
> this should only happen if we're kexec'ing a crash kernel and
> smp_crash_stop_failed(). Is that something we need to care about?

I observed the hang trying to kexec a crash kernel and I did not see the
warning that smp_crash_stop_failed(). I'm not exactly sure why
flush_icache_range() hung (but it did), but I think that
__flush_icache_range() makes more sense here anyway.

> 
> Will
> 
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> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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