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From:   Andy Lutomirski <luto@kernel.org>
Date:   Mon, 1 Feb 2021 08:58:27 -0800
Message-ID: <CALCETrWrj0LJaHTdrydH-i_OkjDb1VF76aJrAWpHA5PL2npezg@mail.gmail.com>
Subject: Re: [PATCH v2] x86/fault: Send a SIGBUS to user process always for
 hwpoison page access.
To:     Aili Yao <yaoaili@kingsoft.com>
Cc:     Tony Luck <tony.luck@intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        naoya.horiguchi@nec.com, "H. Peter Anvin" <hpa@zytor.com>,
        X86 ML <x86@kernel.org>, YANGFENG1@kingsoft.com,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Mon, Feb 1, 2021 at 12:17 AM Aili Yao <yaoaili@kingsoft.com> wrote:
>
> When one page is already hwpoisoned by AO action, process may not be
> killed, the process mapping this page may make a syscall include this
> page and result to trigger a VM_FAULT_HWPOISON fault, if it's in kernel
> mode it may be fixed by fixup_exception. Current code will just return
> error code to user process.
>
> This is not sufficient, we should send a SIGBUS to the process and log
> the info to console, as we can't trust the process will handle the error
> correctly.

Does this happen when one process gets SIGBUSed due to memory failure
and another process independently hits the poisoned memory?  I'm not
entirely convinced that this is a problem.

In any case, this patch needs rebasing on top of my big fault series
-- as it stands, it's way too difficult to keep track of which paths
even call your new code..  And the various signal paths need to be
consolidated -- we already have three of them, and the last thing we
need is a fourth.