linux-kernel - Re: 2f47e7e19f ("x86/mm/kaiser: Use PCID feature to make user and .."): WARNING: CPU: 0 PID: 1 at mm/early_ioremap.c:114 __early

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Date:   Mon, 27 Nov 2017 10:28:35 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Eduardo Valentin <eduval@...zon.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        kernel test robot <fengguang.wu@...el.com>, LKP <lkp@...org>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>, wfg@...ux.intel.com,
        aliguori@...zon.com
Subject: Re: 2f47e7e19f ("x86/mm/kaiser: Use PCID feature to make user and
 .."): WARNING: CPU: 0 PID: 1 at mm/early_ioremap.c:114 __early_ioremap

On 11/27/2017 10:03 AM, Eduardo Valentin wrote:
> On top of VM crashes, on your branch:
> https://git.kernel.org/pub/scm/linux/kernel/git/daveh/x86-kaiser.git/log/?h=kaiser-414-tipwip-20171123
> 
> I am also getting crashes in early userspace, during tlb flushes. When KAISER is enabled and whenever userspace is loaded, I get a stack trace around __do_page_fault() called from restore_regs_and_return_to_kernel(). I saw this very same behavior in your v3 branch (kaiser-414-tipwip-20171121) too.
> 
> The crashes are followed by a machine halt via NMI. They also get the following warning:
>  WARNING: can't dereference iret registers at fffffffffe198048 for ip page_fault+0x11/0x60

There was a known bug in my branch with not mapping some of the
interrupt entry routines.  Random alignment makes it break or work.

Ingo/Thomas, correct me if I'm wrong, but I think we need folks testing
here at the moment:

> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=auto-latest

My tree from last week is ancient gunk at this point. :)