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

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Message-ID: <20180730163938.46zwa7bof7jonako@armageddon.cambridge.arm.com>
Date:   Mon, 30 Jul 2018 17:39:39 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Will Deacon <will.deacon@....com>
Cc:     AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        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 Mon, Jul 30, 2018 at 05:22:35PM +0100, 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 guess we still need to be able to kexec the crash kernel to get as
much information as we can about the failure.

-- 
Catalin