[Xen-devel] Status of HVM improvements, support of recent technologies and request for some tips

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Some years ago the support/improvement of hvm domUsseemed neglected, 
recently seems to be good.
Qemu upstream when I started using early versions from the 1.2 was 
neglected but now it seems early to be quite used, tested and 
considered, thanks to all those who are working to improve support for xen.
New windows pv driversseems to be well alignedwith several improvements.
I found many bugs at the beginning but thanks to Paul Durrant have been 
resolved quickly.
Will be an official xen project build withsigned drivers out there?

OVMF (eufi firmware for hvm domUs) support some years ago was bad but 
now with contribution of Anthony Perard and Wei Lui seems usable with 
windows and linux domUs.
On my latest fast tests I found that boot option is not working or not 
supported for now as I reported in another mail.
Should I report it to ovmf upstream?
In boot tests I saw also floppy test that should be not present based on 
qemu settings: is it only a boot test or is there a bug about it?
I'll test it further and I'll compare with seabios about some small 
strange things I found.
Actuallywhere a system binaries are specified they will not update 
automatically hvmloader built-in seabios and ovmf firmware but require 
xen rebuild (probably major for production system from distro build).
I saw in wiki project "Improvements to firmware handling HVM guests" 
that include also it, is there any news about?
Another probably good thing should be unified eufi and bios support in 
hvmloader.
I saw in wiki project "OVMF Compatibility Support Module support in 
Xen", is there any news about?

Another interesting thing is Q35 support.
Now we are still using very old emulated hardware based on I440FX emulation.
Q35 adds emulation for the ICH9 host chipset, PCI-E bus by default, ahci 
disk controller by default and other things probably useful on recent 
systems.
I did a fast tests with it on xen 2 years ago but I was blocked by disk 
not visible that was require new qemu parameters and that had a bug about.
With a basic ahci support in libxl (included in 4.6) and another patch 
to convert other disk cases (I'll keep it tested and I'll repost for 
4.7) seems that now is possible use new qemu parameters for disks, and 
I'll now retry Q35 on xen.
I'll probably start to write some libxl patches about and I have some 
questions:
Have someone already start to do it but without posting the patches for now?
About xl parameter for chipset selection what is the correct parameter 
to add? device_model_machine="q35|i440fx" (default="i440fx") can be good?
I did a fast look to in libxl_dm.c and I don't know what to do for q35 
case of xen_platform_pci=0. Actually "-machine xenfv" is used but it 
seems only for old chipset case. Any idea/advice?
AHCI disks controller is the default built-in in q35 instead of ide one 
for old chipset. Is it correct to force hdtype="ahci" with q35 and add a 
warning if user selects hdtype="ide"?
If I remember well, is old pci bridge still needed 
("-device","i82801b11-bridge") for emulated vgas support along other 
things or did something changed in the meanwhile?
About hvmloader also this time I'll remove an assert (if I remember 
good) to do q35 tests but a better change is needed and I don't know about.
Any help is appreciated.


Thanks for any reply and sorry for my bad english.

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