linux-kernel - Re: [PATCH] reboot: extend delay from 50us to 50ms for CF9 reboot

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Message-ID: <20170601135940.71e1d212@alans-desktop>
Date:   Thu, 1 Jun 2017 13:59:40 +0100
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     "Shi, FengX" <fengx.shi@...el.com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "matjaz.hegedic@...il.com" <matjaz.hegedic@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Li, Fei" <fei.li@...el.com>,
        "xlpang@...hat.com" <xlpang@...hat.com>,
        "Gortmaker, Paul (Wind River)" <paul.gortmaker@...driver.com>,
        "alex.hung@...onical.com" <alex.hung@...onical.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] reboot: extend delay from 50us to 50ms for CF9 reboot

On Thu, 1 Jun 2017 02:52:32 +0000
"Shi, FengX" <fengx.shi@...el.com> wrote:

> On some emulator system, 50us is not enough to reboot the system
> when write reboot_code to cf9. System will halt there by int3.

Then your emulator is not emulating 8) and you really need to get whoever
is responsible to fix it. If it's some kind of Intel internal emulator
then I don't see why a hack for it belongs upstream either.

You can also use existing boot options to force an EFI, ACPI or BIOS
reboot with a standard kernel so you can deal with your emulator in your
emulator firmware just fine.

> Here extend the delay time from 50us to 50ms.
> Such extension will improve the robustness of reboot,
> without impact to the time of system reboot, which is already triggered by outb.

On a system where a PCI reboot fails you add 50ms before the triple fault
kicks in, so that statement is not true.

Alan