linux-kernel - Re: [PATCH] x86: kmsan: fix boot failure due to instrumentation

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Date: Fri, 8 Mar 2024 14:10:54 +0800
From: Changbin Du <changbin.du@...wei.com>
To: Borislav Petkov <bp@...en8.de>
CC: Changbin Du <changbin.du@...wei.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, Andy Lutomirski
	<luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, "H. Peter Anvin"
	<hpa@...or.com>, Alexander Potapenko <glider@...gle.com>, Andrew Morton
	<akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
	<kasan-dev@...glegroups.com>
Subject: Re: [PATCH] x86: kmsan: fix boot failure due to instrumentation

On Fri, Mar 08, 2024 at 06:45:32AM +0100, Borislav Petkov wrote:
> On Fri, Mar 08, 2024 at 12:44:01PM +0800, Changbin Du wrote:
> > Instrumenting sev.c and mem_encrypt_identity.c with KMSAN will result in
> > kernel being unable to boot. Some of the code are invoked too early in
> > boot stage that before kmsan is ready.
> 
> How do you trigger this?
>
I run the kernel in qemu. One of the calltrace is:
(gdb) bt
#0  find_cc_blob (bp=0x14700 <exception_stacks+30464>) at arch/x86/kernel/sev.c:2067
#1  0x0000000003daeaab in snp_init (bp=0x14700 <exception_stacks+30464>) at arch/x86/kernel/sev.c:2098
#2  0x0000000003db3d69 in sme_enable (bp=0x14700 <exception_stacks+30464>) at arch/x86/mm/mem_encrypt_identity.c:516
#3  0x000000000100003e in startup_64 () at arch/x86/kernel/head_64.S:99
#4  0x0000000000000000 in ?? ()

find_cc_blob() has instrumentation enabled and panic when accessing shadow
memory.

> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette

-- 
Cheers,
Changbin Du