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Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request |
Date: |
Fri, 28 Apr 2017 13:05:43 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.0 |
On 04/28/2017 11:09 AM, Dr. David Alan Gilbert wrote:
>>> At a higher level, using your tags, I'm not sure where a reset triggered
>>> by a fault detected by the hypervisor lives - e.g. an x86 triple fault
>>> where the guest screws up so badly that it just gets reset. Is
>>> that a guest-reset or a guest-panic or what - neither case
>>> was actually asked for by the guest itself.
>>
>> Wouldn't that be host-error (qemu detected an error that prevents
>> further execution of the guest without a reset - and a triple fault
>> seems to fall into the category of the guest getting itself wedged
>> rather than actually trying to reset)? Except patch 3 only used
>> SHUTDOWN_TYPE_HOST_ERROR in the xen portion of the patch.
>>
>> So if any x86 expert has an opinion on where triple-fault handling is
>> emulated, and what category should be used there, I'm welcome to
>> tweaking this series.
>
> It's pretty much on the border anyway, I don't think it matters too
> much; it sounds perfectly reasonable.
Actually, reading
https://blogs.msdn.microsoft.com/larryosterman/2005/02/08/faster-syscall-trap-redux/
makes it sound like the triple-fault = reset is exploited by existing OS
(dating back to days of targetting 286 machines), so it is bare-metal
behavior that we have to faithfully emulate as a guest-triggered reset,
and not something where the guest has wedged itself to the point where
qemu can no longer execute the guest.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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- [Qemu-devel] [PATCH v5 0/4] event: Add source information to SHUTDOWN, Eric Blake, 2017/04/27
- [Qemu-devel] [PATCH v5 1/4] shutdown: Simplify shutdown_signal, Eric Blake, 2017/04/27
- [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Eric Blake, 2017/04/27
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Dr. David Alan Gilbert, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Eric Blake, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Dr. David Alan Gilbert, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Eric Blake, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Dr. David Alan Gilbert, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request,
Eric Blake <=
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Dr. David Alan Gilbert, 2017/04/28
- Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Markus Armbruster, 2017/04/28
Re: [Qemu-devel] [PATCH v5 2/4] shutdown: Prepare for use of an enum in reset/shutdown_request, Markus Armbruster, 2017/04/28
[Qemu-devel] [PATCH v5 4/4] RFC: shutdown: Expose full ShutdownCause across QMP, Eric Blake, 2017/04/27
[Qemu-devel] [PATCH v5 3/4] shutdown: Add source information to SHUTDOWN and RESET, Eric Blake, 2017/04/27