From: Laszlo Ersek <lersek@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Sergio Lopez Pascual <slp@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [RFC] virtio-mmio: implement modern (v2) personality (virtio-1)
Date: Fri, 2 Aug 2019 02:26:28 +0200 [thread overview]
Message-ID: <9b2acff6-8c6d-3aa0-8020-d6d831222496@redhat.com> (raw)
In-Reply-To: <9953cc99-80b3-814c-f75e-a16c987c23e5@redhat.com>
On 08/01/19 01:58, Paolo Bonzini wrote:
> On 30/07/19 18:06, Laszlo Ersek wrote:
>> On 07/29/19 14:57, Sergio Lopez wrote:
>>> Implement the modern (v2) personality, according to the VirtIO 1.0
>>> specification.
>>>
>>> Support for v2 among guests is not as widespread as it'd be
>>> desirable. While the Linux driver has had it for a while, support is
>>> missing, at least, from Tianocore EDK II, NetBSD and FreeBSD.
>>
>> That's right; not only are there no plans to implement virtio-mmio/1.0
>> for OVMF (to my knowledge), I'd even argue against such efforts.
>>
>> OVMF is a heavy-weight guest firmware, which I see entirely out of scope
>> for "micro VMs". And so virtio-mmio/1.0 would seem like a needless &
>> unwelcome complication, from the OVMF maintainership perspective.
>
> But given that, why not rip out virtio-mmio completely?
Virtio-mmio used to be necessary because "qemu-system-aarch64 -M virt"
lacked a PCI host originally. (The relevant commit is 4ab29b8214cc,
"arm: Add PCIe host bridge in virt machine", 2015-02-13; part of v2.3.0.)
Indeed I don't expect anyone to use virtio-mmio nowadays, and removing
it would simplify both our home-grown VIRTIO_DEVICE_PROTOCOL, and the
virtio drivers.
But it's extra work, not entirely risk-free (regressions), and I can't
tell if someone out there still uses virtio-mmio (despite me thinking
that would be unreasonable). I wouldn't like to see more work sunk into
it either way :)
Laszlo
next prev parent reply other threads:[~2019-08-02 0:27 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 12:57 [Qemu-devel] [RFC] virtio-mmio: implement modern (v2) personality (virtio-1) Sergio Lopez
2019-07-29 13:10 ` no-reply
2019-07-30 7:06 ` Stefan Hajnoczi
2019-07-30 8:34 ` Michael S. Tsirkin
2019-07-31 12:22 ` Sergio Lopez
2019-07-31 19:34 ` Michael S. Tsirkin
2019-07-31 21:22 ` Eduardo Habkost
2019-07-30 10:25 ` Andrea Bolognani
2019-07-30 11:35 ` Cornelia Huck
2019-07-30 12:17 ` Andrea Bolognani
2019-07-30 13:14 ` Cornelia Huck
2019-07-30 20:02 ` Michael S. Tsirkin
2019-07-30 20:18 ` Michael S. Tsirkin
2019-07-31 11:04 ` Sergio Lopez
2019-07-31 13:55 ` Cornelia Huck
2019-07-31 19:06 ` Michael S. Tsirkin
2019-08-01 8:18 ` Cornelia Huck
2019-07-31 11:02 ` Sergio Lopez
2019-08-01 12:17 ` Michael S. Tsirkin
2019-07-30 16:06 ` Laszlo Ersek
2019-07-31 23:58 ` Paolo Bonzini
2019-08-01 19:45 ` Michael S. Tsirkin
2019-08-02 9:24 ` Paolo Bonzini
2019-08-02 0:26 ` Laszlo Ersek [this message]
2019-08-02 9:20 ` Peter Maydell
2019-08-02 22:33 ` Laszlo Ersek
2019-08-01 8:37 ` Sergio Lopez
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