Re: [Qemu-devel] [PATCH v8 4/8] ACPI: Add Virtual Machine Generation ID support

[Ben Warren]

> On Feb 17, 2017, at 8:03 AM, Laszlo Ersek <address@hidden> wrote:
> 
> On 02/17/17 16:33, Ben Warren wrote:
>> 
>>> On Feb 17, 2017, at 2:43 AM, Igor Mammedov <address@hidden 
>>> <mailto:address@hidden>
>>> <mailto:address@hidden <mailto:address@hidden>>> wrote:
>>> 
>>> On Thu, 16 Feb 2017 15:15:36 -0800
>>> address@hidden <mailto:address@hidden> <mailto:address@hidden 
>>> <mailto:address@hidden>> wrote:
>>> 
>>>> From: Ben Warren <address@hidden <mailto:address@hidden> 
>>>> <mailto:address@hidden <mailto:address@hidden>>>
>>>> 
>>>> This implements the VM Generation ID feature by passing a 128-bit
>>>> GUID to the guest via a fw_cfg blob.
>>>> Any time the GUID changes, an ACPI notify event is sent to the guest
>>>> 
>>>> The user interface is a simple device with one parameter:
>>>> - guid (string, must be "auto" or in UUID format
>>>>  xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx)
>>> I've given it some testing with WS2012R2 and v4 patches for Seabios,
>>> 
>>> Windows is able to read initial GUID allocation and writeback
>>> seems to work somehow:
>>> 
>>> (qemu) info vm-generation-id
>>> c109c09b-0e8b-42d5-9b33-8409c9dcd16c
>>> 
>>> vmgenid client in Windows reads it as 2 following 64bit integers:
>>> 42d50e8bc109c09b:6cd1dcc90984339b
>>> 
>>> However update path/restore from snapshot doesn't
>>> here is as I've tested it:
>>> 
>>> qemu-system-x86_64 -device vmgenid,id=testvgid,guid=auto -monitor stdio
>>> (qemu) info vm-generation-id
>>> c109c09b-0e8b-42d5-9b33-8409c9dcd16c
>>> (qemu) stop
>>> (qemu) migrate "exec:gzip -c > STATEFILE.gz"
>>> (qemu) quit
>>> 
>>> qemu-system-x86_64 -device vmgenid,id=testvgid,guid=auto -monitor stdio
>>> -incoming "exec: gzip -c -d STATEFILE.gz"
>>> (qemu) info vm-generation-id
>>> 28b587fa-991b-4267-80d7-9cf28b746fe9
>>> 
>>> guest
>>> 1. doesn't get GPE notification that it must receive
>>> 2. vmgenid client in Windows reads the same value
>>>     42d50e8bc109c09b:6cd1dcc90984339b
>>> 
>> Strange, this was working for me, but with a slightly different test method:
>> 
>>  * I use virsh save/restore
> 
> Awesome, this actually what I should try. All my guests are managed by
> libvirt (with the occasional <qemu:arg>, for development), and direct
> QEMU monitor commands such as
> 
>  virsh qemu-monitor-command ovmf.rhel7 --hmp 'info vm-generation-id'
> 
> only work for me if they are reasonably non-intrusive.
> 
>>  * While I do later testing with Windows, during development I use a
>>    Linux kernel module I wrote that keeps track of GUID and
>>    notifications.  I’m happy to share this with you if interested.
> 
> Please do. If you have a public git repo somewhere, that would be
> awesome. (Bonus points if the module builds out-of-tree, if the
> kernel-devel package is installed.)
> 
Here you go:
https://github.com/ben-skyportsystems/vmgenid-test 
<https://github.com/ben-skyportsystems/vmgenid-test>

I don’t know if something like this would ever be accepted into the Linux 
kernel, but it has been invaluable to me, and I’d like to see it somewhere 
better.

> NB: while the set-id monitor command was part of the series, I did test
> it to the extent that I checked the SCI ("ACPI interrupt") count in the
> guest, in /proc/interrupts. I did see it increase, so minimally the SCI
> injection was fine.
> 
> Thanks!
> Laszlo
> 
>> I’ll dig into this morning.
>> 
>> —Ben
>> <snip>

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