[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [RFC PATCH 0/2] virtio-mmio: add irqfd support for vhos
From: |
Eric Auger |
Subject: |
Re: [Qemu-devel] [RFC PATCH 0/2] virtio-mmio: add irqfd support for vhost-net based on virtio-mmio |
Date: |
Wed, 05 Nov 2014 09:43:47 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
On 10/27/2014 12:23 PM, Li Liu wrote:
>
>
> On 2014/10/27 17:37, Peter Maydell wrote:
>> On 25 October 2014 09:24, john.liuli <address@hidden> wrote:
>>> To get the interrupt reason to support such VIRTIO_NET_F_STATUS
>>> features I add a new register offset VIRTIO_MMIO_ISRMEM which
>>> will help to establish a shared memory region between qemu and
>>> virtio-mmio device. Then the interrupt reason can be accessed by
>>> guest driver through this region. At the same time, the virtio-mmio
>>> dirver check this region to see irqfd is supported or not during
>>> the irq handler registration, and different handler will be assigned.
>>
>> If you want to add a new register you should probably propose
>> an update to the virtio spec. However, it seems to me it would
>> be better to get generic PCI/PCIe working on the ARM virt
>> board instead; then we can let virtio-mmio quietly fade away.
>> This has been on the todo list for ages (and there have been
>> RFC patches posted for plain PCI), it's just nobody's had time
>> to work on it.
>>
>> thanks
>> -- PMM
>>
>
> So you mean virtio-mmio will be replaced by PCI/PCIe on ARM at last?
> If so, let this patch go with the wind:). Thx.
Hi,
As a fix of current situation where ISR is only partially updated when
vhost-irqfd handles standard IRQ and waiting for PCI emuluation,
wouldn't it make sense to store ISR content on vhost driver side and
introduce ioctls to read/write it. When using vhost BE, virtio QEMU
device would use those ioctl to read/update the ISR content. On top of
that we would update the ISR in vhost before triggering the irqfd. If I
do not miss anything this would at least make things functional with irqfd.
As a second step, we could try to introduce in-kernel emulation of
ISR/ACK to fix the performance issue related to going to user-side each
time ISR/ACK accesses are done.
Do you think it is worth investigating this direction?
Thank you in advance
Best Regards
Eric
>
> Li.
>> .
>>
>
>
- Re: [Qemu-devel] [RFC PATCH 0/2] virtio-mmio: add irqfd support for vhost-net based on virtio-mmio,
Eric Auger <=