linux-kernel - Re: [PATCH v5] x86: call smp vmxoff in smp stop

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Date:   Thu, 20 Apr 2017 12:01:33 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     mingo@...nel.org, x86@...nel.org,
        Tiantian Feng <fengtiantian@...wei.com>,
        Xishi Qiu <qiuxishi@...wei.com>
Subject: Re: [PATCH v5] x86: call smp vmxoff in smp stop

On 19.04.2017 18:18, Paolo Bonzini wrote:
> From: Tiantian Feng <fengtiantian@...wei.com>
> 
> A CPU in VMX root mode will ignore INIT signals and fail to bring
> up the APs after reboot.  Therefore, on a panic we disable VMX on all
> CPUs before rebooting or triggering kdump.
> 
> Do this when halting the machine as well, in case a firmware-level reboot
> does not perform a cold reset for all processors.  Without doing this,
> rebooting the host may hang.

Guess this make sense, just wonder if something like that is actually
expected to work? Not doing a cold reset feels like leaving a lot of
stuff in an uninitialized state. Shouldn't that specific firmware then
care about performing any necessary resets?

-- 

Thanks,

David