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Date:   Wed, 30 Aug 2023 23:18:14 +0100
From:   Will Deacon <will@kernel.org>
To:     Shuai Xue <xueshuai@linux.alibaba.com>
Cc:     catalin.marinas@arm.com, James.Bottomley@HansenPartnership.com,
        deller@gmx.de, dave.hansen@linux.intel.com, luto@kernel.org,
        peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, x86@kernel.org, hpa@zytor.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-parisc@vger.kernel.org
Subject: Re: [PATCH] HWPOISON: add a pr_err message when forcibly send a
 sigbus
Message-ID: <20230830221814.GB30121@willie-the-truck>
References: <20230819102212.21103-1-xueshuai@linux.alibaba.com>
 <20230821105025.GB19469@willie-the-truck>
 <44c4d801-3e21-426b-2cf0-a7884d2bf5ff@linux.alibaba.com>
 <54114b64-4726-da46-8ffa-16749ec0887a@linux.alibaba.com>
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On Mon, Aug 28, 2023 at 09:41:55AM +0800, Shuai Xue wrote:
> On 2023/8/22 09:15, Shuai Xue wrote:
> > On 2023/8/21 18:50, Will Deacon wrote:
> >>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> >>> index 3fe516b32577..38e2186882bd 100644
> >>> --- a/arch/arm64/mm/fault.c
> >>> +++ b/arch/arm64/mm/fault.c
> >>> @@ -679,6 +679,8 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr,
> >>>  	} else if (fault & (VM_FAULT_HWPOISON_LARGE | VM_FAULT_HWPOISON)) {
> >>>  		unsigned int lsb;
> >>>  
> >>> +		pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
> >>> +		       current->comm, current->pid, far);
> >>>  		lsb = PAGE_SHIFT;
> >>>  		if (fault & VM_FAULT_HWPOISON_LARGE)
> >>>  			lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
> >>
> >> Hmm, I'm not convinced by this. We have 'show_unhandled_signals' already,
> >> and there's plenty of code in memory-failure.c for handling poisoned pages
> >> reported by e.g. GHES. I don't think dumping extra messages in dmesg from
> >> the arch code really adds anything.
> > 
> > I see the show_unhandled_signals() will dump the stack but it rely on
> > /proc/sys/debug/exception-trace be set.
> > 
> > The memory failure is the top issue in our production cloud and also other hyperscalers.
> > We have received complaints from our operations engineers and end users that processes
> > are being inexplicably killed :(. Could you please consider add a message?

I don't have any objection to logging this stuff somehow, I'm just not
convinced that the console is the best place for that information in 2023.
Is there really nothing better?

Will