linux-kernel - Re: [x86] 5ac0c41bf3: WARNING: CPU: 0 PID: 0 at arch/x86/mm/extable.c:50 ex_handler_rdmsr

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Date:	Wed, 15 Jun 2016 20:23:32 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Paolo Bonzini <pbonzini@...hat.com>, wfg@...ux.intel.com,
	LKP <lkp@...org>, lkml <linux-kernel@...r.kernel.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Eduardo Habkost <ehabkost@...hat.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [x86] 5ac0c41bf3: WARNING: CPU: 0 PID: 0 at
 arch/x86/mm/extable.c:50 ex_handler_rdmsr_unsafe

On Wed, Jun 15, 2016 at 11:12:37AM -0700, Andy Lutomirski wrote:
> I want to see actual_problem in the log.

So the optimal thing to do for that is to return an error to the calling
site which says "exception got handled" and then the *calling* site can
dump_stack().

And the old code did that:

static inline unsigned long long native_read_msr_safe(unsigned int msr,
                                                      int *err)
{
        DECLARE_ARGS(val, low, high);

        asm volatile("2: rdmsr ; xor %[err],%[err]\n"
                     "1:\n\t"
                     ".section .fixup,\"ax\"\n\t"
                     "3:  mov %[fault],%[err] ; jmp 1b\n\t"
                     ".previous\n\t"
                     _ASM_EXTABLE(2b, 3b)
                     : [err] "=r" (*err), EAX_EDX_RET(val, low, high)
                     : "c" (msr), [fault] "i" (-EIO));
						^^^^


-- 
Regards/Gruss,
    Boris.

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