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Date:   Tue, 14 May 2019 13:38:26 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Dave Young <dyoung@redhat.com>
Cc:     Baoquan He <bhe@redhat.com>, Borislav Petkov <bp@alien8.de>,
        j-nomura@ce.jp.nec.com, kasong@redhat.com,
        fanc.fnst@cn.fujitsu.com, x86@kernel.org,
        kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
        hpa@zytor.com, tglx@linutronix.de
Subject: Re: [PATCH v6 1/2] x86/kexec: Build identity mapping for EFI systab
 and ACPI tables
Message-ID: <20190514113826.GM2589@hirez.programming.kicks-ass.net>
References: <20190424092944.30481-2-bhe@redhat.com>
 <20190429002318.GA25400@MiWiFi-R3L-srv>
 <20190429135536.GC2324@zn.tnic>
 <20190513014248.GA16774@MiWiFi-R3L-srv>
 <20190513070725.GA20105@zn.tnic>
 <20190513073254.GB16774@MiWiFi-R3L-srv>
 <20190513075006.GB20105@zn.tnic>
 <20190513080653.GD16774@MiWiFi-R3L-srv>
 <20190514032208.GA25875@dhcp-128-65.nay.redhat.com>
 <20190514084841.GA27876@dhcp-128-65.nay.redhat.com>
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On Tue, May 14, 2019 at 04:48:41PM +0800, Dave Young wrote:

> > I did some tests on the laptop,  thing is:
> > 1. apply the 3 patches (two you posted + Boris's revert commit 52b922c3d49c)
> >    on latest Linus master branch, everything works fine.
> > 
> > 2. build and test the tip/next-merge-window branch, kernel hangs early
> > without output, (both 1st boot and kexec boot)
> 
> Update about 2.  It should be not early rsdp related, I got the boot log
> Since can not reproduce with Linus master branch it may have been fixed.

Nothing was changed here since PTI.

> [    0.685374][    T1] rcu: Hierarchical SRCU implementation.
> [    0.686414][    T1] general protection fault: 0000 [#1] SMP PTI
> [    0.687328][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.1.0-rc6+ #877
> [    0.687328][    T1] Hardware name: LENOVO 4236NUC/4236NUC, BIOS 83ET82WW (1.52 ) 06/04/2018
> [    0.687328][    T1] RIP: 0010:reserve_ds_buffers+0x34e/0x450

> [    0.687328][    T1] Call Trace:
> [    0.687328][    T1]  ? hardlockup_detector_event_create+0x50/0x50
> [    0.687328][    T1]  x86_reserve_hardware+0x173/0x180
> [    0.687328][    T1]  x86_pmu_event_init+0x39/0x220

The DS buffers are special in that they're part of cpu_entrt_area. If
this comes apart it might mean your pagetables are dodgy.