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

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Date:   Wed, 27 Jan 2021 14:30:39 +0000
From:   Andrew Cooper <andrew.cooper3@...rix.com>
To:     Jürgen Groß <jgross@...e.com>,
        <xen-devel@...ts.xenproject.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
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>
Subject: Re: [PATCH v2] x86/xen: avoid warning in Xen pv guest with
 CONFIG_AMD_MEM_ENCRYPT enabled

On 27/01/2021 13:59, Jürgen Groß wrote:
> On 27.01.21 12:23, Andrew Cooper wrote:
>> On 27/01/2021 10:26, 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 *?
>>
>> Yes, but I was assuming that they both contained the same information.
>>
>>>
>>> So I have no idea how I should get this information without creating
>>> a per-vector handler.
>>
>> Oh - that's dull.
>>
>> Fine then.  Reviewed-by: Andrew Cooper <andrew.cooper3@...rix.com>
>>
>
> I think I'll switch the panic() to printk(); BUG(); in order to have
> more diagnostic data. Can I keep your R-b: with that modification?

Yeah.  Sounds good.

~Andrew