Hi Lazlo,
On 06/03/2020 22:14, Laszlo Ersek wrote:
Hi Nikita,
On 03/04/20 20:22, Nikita Leshenko wrote:
This series adds driver support for:
- LSI53C1030
- SAS1068
- SAS1068E
These controllers are widely supported by QEMU, VirtualBox and VMWare.
This work is part of the more general agenda of enhancing OVMF boot
device support to have feature parity with SeaBIOS.
We have also developed support for PVSCSI which we will submit in a
separate patch series.
I'd like to learn more of this general agenda ("feature parity with
SeaBIOS"). I have never felt the need for any SCSI controller offered by
QEMU other than virtio-scsi.
Because you guys are contributing Fusion-MPT and PVSCSI to OVMF,
obviously such a practical need must exist ("feature parity with
SeaBIOS" is vague, I'm not really buying it :) ).
The motivation behind supporting booting from these devices is being
able to run VMs that originally run on other hypervisors, such as VMware
ESXi, on top of QEMU/KVM without any changes to the image (In contrast
to approaches such as virt-v2v, Amazon CloudEndure or Google
Velostrata). This technology was developed in Ravello Systems (Acquired
by Oracle), which offered a product to run VMware-based images on top of
any public cloud without any modification to the VMs.
This is also why you would also see QEMU PVSCSI device emulation and
SeaBIOS PVSCSI driver were contributed by Ravello as-well.
Similar work to Ravello was done by Virtuozzo for Hyper-V based VMs (See
their enhancements to QEMU of emulating Hyper-V PV devices). They also
have EDK2 drivers for these devices that are not upstream.
Having said that, it is true that these two patch-series provide feature
parity with SeaBIOS. I do believe that it makes sense OVMF will support
booting from any storage device that QEMU is able to emulate. Especially
if SeaBIOS is already able to boot from that device as-well.
So I have two requests:
(1) please describe the actual use case (hypervisor, guest OS, maybe
performance, etc) for these drivers, in the associated bugzilla,
I don't think the description we have written in the relevant BugZilla
tickets should change much. It's still true that these are contributed
as part of feature-parity with SeaBIOS and allowing to boot from these
devices. How one use this depends on it's own use-case. It could be to
be able to boot VMware-based VMs as-is under QEMU/KVM, but it could also
be used to boot a VM with a PVSCSI controller that was originally
created with QEMU/KVM.
This is similar to upstream commit c137d9508169 ("OvmfPkg/QemuVideoDxe:
VMWare SVGA device support") which added support for VMware-SVGA GPU.
(2) please make the inclusion of these drivers in the OVMF DSC and FDF
files dependent on a new build flag (-D). It's up to you whether you
want to gate PVSCSI and Fusion-MPT with the same flag, or if you want to
assign separate flags to them.
It's fine if the default value is TRUE, for that flag (those flags). I'm
asking for them from a downstream perspective -- some distros follow a
"we ship it, we support it" model, and so they must be careful with
rebases to new usptream releases. I'd like to permit such downstreams to
easily disable these drivers, with just -D flags, without
downstream-only patches for the OVMF DSC and FDF files, that might need
repeated downstream rebasing and review.
Again, it's perfectly fine if the upstream defaults are TRUE.
... If you feel tempted to point out the Xen paravirt drivers: you are
entirely right, but those are already covered by
<https://urldefense.com/v3/__https://bugzilla.tianocore.org/show_bug.cgi?id=2122__;!!GqivPVa7Brio!JJpn5PCAL9AX7xdt4qLhQJMF7L19-QEEbGF_o9bHTGsccK6a5AeDD0-_j3_UPCk$
>.
Funny. I was about to point out that the Xen PV drivers are not
conditioned by any flag! :)
OK. I think it's appropriate we will add a separate flag for each device
and make them both TRUE by default (As I think should be appropriate for
any device built-in by default into QEMU).
Thanks,
-Liran
Thanks!
Laszlo
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