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Subject: Re: [crash] PANIC: double fault, error_code: 0x0
To: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org,
        Andy Lutomirski <luto@kernel.org>
References: <20171124172411.19476-1-mingo@kernel.org>
 <20171124202237.oytdkqq25s3ak2ul@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>,
        Linus Torvalds <torvalds@linux-foundation.org>
From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <94d21124-6193-6bb3-3f81-e2005ab7e7d2@linux.intel.com>
Date: Fri, 24 Nov 2017 20:09:37 -0800
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On 11/24/2017 12:22 PM, Ingo Molnar wrote:
> [    8.831002] RIP: 0010:page_fault+0x11/0x60
> [    8.831002] RSP: 0000:ffffffffff0e7fc8 EFLAGS: 00010046
> [    8.831002] RAX: 00000000819d4d77 RBX: 0000000000000001 RCX: ffffffff819d4d77
> [    8.831002] RDX: 0000000000000003 RSI: 0000000000000010 RDI: ffffffffff0e8078
> [    8.831002] RBP: 0000000000000000 R08: 00007ffd7f1aa530 R09: 00007f9407f98400
> [    8.831002] R10: 0000000000000007 R11: 0000000000000000 R12: 00007ffd7f1aa680
> [    8.831002] R13: 00007f9407f91f80 R14: 0000000000000007 R15: 0000000000000000
> [    8.831002]  ? native_iret+0x7/0x7
> [    8.831002] WARNING: can't dereference iret registers at ffffffffff0e8048 for ip page_fault+0x11/0x60
> [    8.831002]  </#DF>
> [    8.831002]  <SYSENTER>
> [    8.831002]  ? __do_page_fault+0x4c0/0x4c0
> [    8.831002]  ? page_fault+0x2c/0x60
> [    8.831002]  ? native_iret+0x7/0x7
> [    8.831002]  ? __do_page_fault+0x4c0/0x4c0
> [    8.831002]  ? page_fault+0x2c/0x60
> [    8.831002]  ? __entry_text_end+0x1/0x1
> [    8.831002]  </SYSENTER>

Just a stab in the dark from looking at this for a few seconds...

Doesn't this stack trace mean we started C-code page fault handing on
the sysenter stack?  Seems like we missed a switch to the process stack.