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

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Date:   Mon, 30 Jul 2018 17:22:35 +0100
From:   Will Deacon <will.deacon@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Dave Kleikamp <dave.kleikamp@...cle.com>,
        linux-arm-kernel@...ts.infradead.org,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] arm64: kexec: machine_kexec should call
 __flush_icache_range

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?

Will