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Date: Fri, 8 Mar 2024 14:10:54 +0800
From: Changbin Du <changbin.du@huawei.com>
To: Borislav Petkov <bp@alien8.de>
CC: Changbin Du <changbin.du@huawei.com>, Thomas Gleixner
	<tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Dave Hansen
	<dave.hansen@linux.intel.com>, <x86@kernel.org>, Andy Lutomirski
	<luto@kernel.org>, Peter Zijlstra <peterz@infradead.org>, "H. Peter Anvin"
	<hpa@zytor.com>, Alexander Potapenko <glider@google.com>, Andrew Morton
	<akpm@linux-foundation.org>, <linux-kernel@vger.kernel.org>,
	<kasan-dev@googlegroups.com>
Subject: Re: [PATCH] x86: kmsan: fix boot failure due to instrumentation
Message-ID: <20240308061054.54zxik32u4w2bynd@M910t>
References: <20240308044401.1120395-1-changbin.du@huawei.com>
 <20240308054532.GAZeql_HPGb5lAU-jx@fat_crate.local>
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In-Reply-To: <20240308054532.GAZeql_HPGb5lAU-jx@fat_crate.local>

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