linux-kernel - Re: [PATCH v2] x86/xen: avoid warning in Xen pv guest with CONFIG_AMD_MEM

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Message-ID: <a83aa5b1-87b7-bed3-e462-6bd5f854757c@suse.com>
Date:   Wed, 27 Jan 2021 12:06:43 +0100
From:   Jan Beulich <jbeulich@...e.com>
To:     Jürgen Groß <jgross@...e.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org, Andrew Cooper <andrew.cooper3@...rix.com>,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org
Subject: Re: [PATCH v2] x86/xen: avoid warning in Xen pv guest with
 CONFIG_AMD_MEM_ENCRYPT enabled

On 27.01.2021 11:26, Jürgen Groß wrote:
> On 27.01.21 10:43, Andrew Cooper wrote:
>> On 27/01/2021 09:38, Juergen Gross wrote:
>>> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
>>> index 4409306364dc..ca5ac10fcbf7 100644
>>> --- a/arch/x86/xen/enlighten_pv.c
>>> +++ b/arch/x86/xen/enlighten_pv.c
>>> @@ -583,6 +583,12 @@ DEFINE_IDTENTRY_RAW(xenpv_exc_debug)
>>>   		exc_debug(regs);
>>>   }
>>>   
>>> +DEFINE_IDTENTRY_RAW(exc_xen_unknown_trap)
>>> +{
>>> +	/* This should never happen and there is no way to handle it. */
>>> +	panic("Unknown trap in Xen PV mode.");
>>
>> Looks much better.  How about including regs->entry_vector here, just to
>> short circuit the inevitable swearing which will accompany encountering
>> this panic() ?
> 
> You are aware the regs parameter is struct pt_regs *, not the Xen
> struct cpu_user_regs *?
> 
> So I have no idea how I should get this information without creating
> a per-vector handler.

Maybe log _RET_IP_ then (ideally decoded to a symbol), to give at
least some hint as to where this was coming from?

Jan