linux-kernel - Re: [RFC][PATCH 2/8] x86/mm: break out kernel address space handling

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Message-ID: <90a3e9c8-61df-f1dc-0d5c-b71342835f59@linux.intel.com>
Date:   Fri, 7 Sep 2018 15:37:46 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     linux-kernel@...r.kernel.org, sean.j.christopherson@...el.com,
        peterz@...radead.org, tglx@...utronix.de, x86@...nel.org,
        luto@...nel.org
Subject: Re: [RFC][PATCH 2/8] x86/mm: break out kernel address space handling

On 09/07/2018 03:21 PM, Andy Lutomirski wrote:
>> +static void
>> +do_kern_addr_space_fault(struct pt_regs *regs, unsigned long hw_error_code,
>> +             unsigned long address)
>> +{
>
> Can you add a comment above this documenting *when* it’s called? Is
> it all faults, !user_mode faults, or !PF_USER?

Yep, can do.

>> +    /*
>> +     * This is a "bad" fault in the kernel address space.  There
>> +     * is no reasonable explanation for it.  We will either kill
>> +     * the process for making a bad access, or oops the kernel.
>> +     */
> 
> Or call an extable handler?
> 
> Maybe the wording should be less scary, e.g. “this fault is a genuine
> error. Send a signal, call an exception handler, or oops, as
> appropriate.”

Yeah, the real behavior is quite a bit more subtle than I'm letting on.
I'll tone it down.