linux-kernel - Re: [PATCH v3] x86/split_lock: Sanitize userspace and guest error output

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Date:   Mon, 15 Jun 2020 18:51:31 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Tony Luck <tony.luck@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Rahul Tanwar <rahul.tanwar@...ux.intel.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH v3] x86/split_lock: Sanitize userspace and guest error
 output

On Mon, Jun 15, 2020 at 07:39:00AM -0400, Prarit Bhargava wrote:
> There are two problems with kernel messages in fatal mode that were found
> during testing of guests and userspace programs.
> 
> The first is that no kernel message is output when the split lock detector
> is triggered with a userspace program.  As a result the userspace process
> dies from receiving SIGBUS with no indication to the user of what caused
> the process to die.
> 
> The second problem is that only the first triggering guest causes a kernel
> message to be output because the message is output with pr_warn_once().
> This also results in a loss of information to the user.
> 
> While fixing these I noticed that the same message was being output
> three times so I'm cleaning that up too.
> 
> Fix fatal mode output, and use consistent messages for fatal and
> warn modes for both userspace and guests.
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>

This needs a Co-developed-by for me, and your SOB should come last, e.g.

  Co-developed-by: Sean Christopherson <sean.j.christopherson@...el.com> 
  Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
  Signed-off-by: Prarit Bhargava <prarit@...hat.com>

See "12) When to use Acked-by:, Cc:, and Co-developed-by:" in
Documentation/process/submitting-patches.rst for more details.