linux-kernel - Re: [Xen-devel] [PATCH 2/5] xen/x86-64: clean up warnings aboutIST-using traps

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Date:	Fri, 08 May 2009 08:23:01 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 2/5] xen/x86-64: clean up warnings	 aboutIST-using
 traps

Jan Beulich wrote:
>> else if (addr == (unsigned long)int3)
>> 		addr = (unsigned long)xen_int3;
>> -	else
>> -		WARN_ON(val->ist != 0);
>> +	else if (addr == (unsigned long)double_fault ||
>> +		 addr == (unsigned long)stack_segment) {
>>     
>
> I don't think you want to exclude handling stack faults: Ordinary memory
> references using rsp or rbp as the base register will cause these instead
> of general protection faults when the resulting effective address is non-
> canonical.
>   

So even usermode memory accesses?  Ew.  Well, we can run the trap 
handler on the normal kernel stack in that case.  I'll cook something up.

    J
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