Re: [PATCH kvmtool v2 00/13] Implement reset of virtio devices

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On 22/01/2019 07:07, Will Deacon wrote:
> On Thu, Jan 10, 2019 at 02:12:37PM +0000, Julien Thierry wrote:
>> This series was developped by Jean-Philippe and is needed for a series
>> I'll be posting shortly after to load firmwares on arm kvmtool.
>>
>> Currently, when a guest tries to reset a device, a lot of ressources
>> aren't reset (threads keep running, virtio queue keep their state, etc).
>>
>> When the guest only does the reset to initialize the device and there
>> were no previous users, there is no noticeable issue. But when a guest
>> has a firmare + Linux, if the firmware uses a virtio device, Linux will
>> fail to probe that device.
>>
>> This series aim to properly reset the virtio resources when the guests
>> requests it.
>>
>> Reset of net vhost is unsupported for now.
>>
>> Patch 1 is a bug fix on ioeventfd
>> Patch 2-6 provide the core support so devices can implement their reset
>> Patch 7-13 implements the reset for the various virtio devices
> 
> Cheers, I'll pick this up. There's a vague comment in patch 10 about aio
> being busted. If that's the case then we should either fix it or remove
> it...

Thanks! I think my main concern with aio was that the iocb structures
are allocated on the stack, and get trashed after io_submit(). The aio
man says that control block should remain valid until the I/O completes
(which might still apply even if we're using raw iocb instead of aiocb -
I can't find where the kernel copies those buffers). I'll take a better
look and implement reset if possible.

Thanks,
Jean
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