linux-kernel - Re: KVM guest sometimes failed to boot because of kernel stack overflow if KPTI is enabled on a hisilicon ARM64 platform.

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Date:   Wed, 27 Jun 2018 09:39:36 +0100
From:   James Morse <james.morse@....com>
To:     Wei Xu <xuwei5@...ilicon.com>
Cc:     Will Deacon <will.deacon@....com>, mark.rutland@....com,
        catalin.marinas@....com, Linuxarm <linuxarm@...wei.com>,
        Zhangyi ac <zhangyi.ac@...wei.com>, suzuki.poulose@....com,
        marc.zyngier@....com,
        "Xiongfanggou (James)" <james.xiong@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dave.martin@....com,
        "Liyuan (Larry, Turing Solution)" <Larry.T@...wei.com>,
        libeijian@...ilicon.com
Subject: Re: KVM guest sometimes failed to boot because of kernel stack
 overflow if KPTI is enabled on a hisilicon ARM64 platform.

Hi Wei,

On 26/06/18 18:47, Will Deacon wrote:
> On Wed, Jun 27, 2018 at 01:16:44AM +0800, Wei Xu wrote:
>>     [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x480fd010]
>>     [    0.000000] Linux version 4.18.0-rc2-58583-g7daf201-dirty
> 
> I'm still suspicious that this is 4.18-rc2 with "no change on top" ^^^ !

Some examples:

For comparison, when I boot v4.17 it looks like this:
| Linux version 4.17.0 (morse@...chizedek) (gcc version 4.9.3 20141031
| (prerelease) (Linaro GCC 2014.11)) #9886 SMP PREEMPT Thu Jun 21 10:30:55 BST
| 2018


If I apply some extra patches and make some uncommitted changes, it looks like this:
| Linux version 4.17.0-00025-ga22ca2234824-dirty (morse@...chizedek) (gcc
| version 4.9.3 20141031 (prerelease) (Linaro GCC 2014.11)) #9887 SMP PREEMPT
| Thu Jun 21 10:46:22 BST 2018


Hence we read your '4.17.0-45864-g29dcea8-dirty' line as v4.17 with extra
patches and uncommited changes, and similar with this v4.18-rc2.

I agree 7daf201 is the head commit for v4.18-rc2, but something has gone wrong
here. Could you try building from a fresh clone of Linus' tree?

(I suspect at some point you've applied a patch, and have then been merging
upstream, instead of 'fast forwarding')



Thanks,

James