linux-kernel - Re: [Question PATCH kernel] x86/amd/sev/nmi+vc: Fix stack handling (why is this happening?)

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Message-ID: <b7880f0b-a592-cf2d-03b9-1ccfd83f8223@amd.com>
Date:   Fri, 27 Jan 2023 22:56:26 +1100
From:   Alexey Kardashevskiy <aik@....com>
To:     Joerg Roedel <joro@...tes.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Jiri Kosina <jkosina@...e.cz>, Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [Question PATCH kernel] x86/amd/sev/nmi+vc: Fix stack handling
 (why is this happening?)



On 27/1/23 21:37, Joerg Roedel wrote:
> On Fri, Jan 27, 2023 at 10:08:14AM +0100, Peter Zijlstra wrote:
>> Welcome to the wonderful shit show that is x86 exceptions :/
>>
>> I thought sev_es_*() is supposed to fix this. Joerg, any clue?
> 
> Hmm, no, not yet, the stack-trace doesn't make much sense to me. The
> sev_es_* function calls in the NMI path are for re-enabling NMI and
> adjusting the #VC IST stack to allow nested VCs.
> 
> Alexey, can you try to get a more stable backtrace? For example by
> building the kernel with frame pointers?

Do you mean these guys (below)?

aik@...-Standard-PC-i440FX-PIIX-1996:~$ grep FRAME_POINTER 
/boot/config-$(uname -r)
CONFIG_SCHED_OMIT_FRAME_POINTER=y 

CONFIG_FRAME_POINTER=y 

CONFIG_UNWINDER_FRAME_POINTER=y


Here is the complete output of that VM (200k so not in the email):

https://github.com/aik/linux/commit/d0d6bbb58fcd927ddd1f8e9d42ab121920c7eafc

Note that the original long backtrace appears more than once, I just did 
not copy all of that in the first email.

-- 
Alexey