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[Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property |
Date: |
Mon, 14 Dec 2009 13:10:47 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Mon, Dec 14, 2009 at 11:24:41AM +0100, Gerd Hoffmann wrote:
> On 12/14/09 10:42, Michael S. Tsirkin wrote:
>> On Mon, Dec 14, 2009 at 10:41:26AM +0100, Gerd Hoffmann wrote:
>>> On 12/13/09 21:43, Michael S. Tsirkin wrote:
>>>> Add features property to virtio. This makes it
>>>> possible to e.g. define machine without indirect
>>>> buffer support, which is required for 0.10
>>>> compatibility. or without hardware checksum
>>>> support, which is required for 0.11 compatibility.
>>>
>>> I'd suggest to add flags for the individual features to the drivers
>>> which actually use it instead, so you'll have
>>>
>>> -device virtio-net-pci,hw-checksum=0
>>>
>>> and
>>>
>>> -device virtio-blk-pci,indirect-buffers=0
>>>
>>> cheers,
>>> Gerd
>>
>> Hmm. I hoped to avoid it, there are lots of features so it's a lot of
>> work and in practice, this will most likely be set by machine
>> description ...
>
> MSI-X aka vectors property is already done this way, so I'd tend to
> continue this way. It is also more user friendly. Sure, these are most
> likely not used on a daily base by users, but being able to turn off --
> say -- indirect buffers for testing and/or bug hunting reasons without
> having to construct magic hex numbers from virtio header files would be
> nice.
>
> Can you give a list of features? The patch description sounded like it
> is just the two listed above ...
>
> cheers,
> Gerd
Heh, it's a long list.
transport features (common to all):
VIRTIO_F_NOTIFY_ON_EMPTY;
VIRTIO_RING_F_INDIRECT_DESC;
VIRTIO_F_BAD_FEATURE; <- not sure we need a flag for this
for net:
uint32_t features = (1 << VIRTIO_NET_F_MAC) |
(1 << VIRTIO_NET_F_MRG_RXBUF) |
(1 << VIRTIO_NET_F_STATUS) |
(1 << VIRTIO_NET_F_CTRL_VQ) |
(1 << VIRTIO_NET_F_CTRL_RX) |
(1 << VIRTIO_NET_F_CTRL_VLAN) |
(1 << VIRTIO_NET_F_CTRL_RX_EXTRA);
if (peer_has_vnet_hdr(n)) {
tap_using_vnet_hdr(n->nic->nc.peer, 1);
features |= (1 << VIRTIO_NET_F_CSUM);
features |= (1 << VIRTIO_NET_F_HOST_TSO4);
features |= (1 << VIRTIO_NET_F_HOST_TSO6);
features |= (1 << VIRTIO_NET_F_HOST_ECN);
features |= (1 << VIRTIO_NET_F_GUEST_CSUM);
features |= (1 << VIRTIO_NET_F_GUEST_TSO4);
features |= (1 << VIRTIO_NET_F_GUEST_TSO6);
features |= (1 << VIRTIO_NET_F_GUEST_ECN);
if (peer_has_ufo(n)) {
features |= (1 << VIRTIO_NET_F_GUEST_UFO);
features |= (1 << VIRTIO_NET_F_HOST_UFO);
}
for block:
features |= (1 << VIRTIO_BLK_F_SEG_MAX);
features |= (1 << VIRTIO_BLK_F_GEOMETRY);
if (bdrv_enable_write_cache(s->bs))
features |= (1 << VIRTIO_BLK_F_WCACHE);
#ifdef __linux__
features |= (1 << VIRTIO_BLK_F_SCSI);
#endif
if (strcmp(s->serial_str, "0"))
features |= 1 << VIRTIO_BLK_F_IDENTIFY;
if (bdrv_is_read_only(s->bs))
features |= 1 << VIRTIO_BLK_F_RO;
I could try and group features, but this way we
loose in flexibility ...
How about I name properties exactly like virtio macros? e.g.
VIRTIO_BLK_F_IDENTIFY etc? This way maybe I can use preprocessor magic
to reduce duplication ...
Also, I'd like these things to be saved in bits and not add a ton
of fields in device. Ideas how to do this?
--
MST
- [Qemu-devel] [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/13
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property,
Michael S. Tsirkin <=
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Markus Armbruster, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Gerd Hoffmann, 2009/12/14
- Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property, Michael S. Tsirkin, 2009/12/14