[Pkg-xen-devel] Bug#910946: Bug#910946: xen-hypervisor-4.11-amd64: HVM DomU - 64-bit kernel cannot access emulated ATA devices

[Stephen Oberholtzer]

On Sat, Oct 13, 2018 at 5:44 PM Hans van Kranenburg <hans at knorrie.org>
wrote:

> 19:35 < andyhhp__> Stevie-O: Thats most likely a dom0 kernel bug
> 19:35 < andyhhp__> the 32 and 64bit block protocols were binarily
> diverged for a while due to some "interesing" bugfixes
> 19:36 < andyhhp__> but its the most common cause of "32bit works, 64bit
> doesn't" when it comes to anything vaguely like disks
>
>

> Since the comments from Andrew point at at least the dom0 kernel version
> being a factor in this equation: can you also add linux kernel version
> information for dom0 and domU for your tests? These kind of things
> explode into a testing-matrix of combinations of things very fast, and
> any testing you can do providing that info will help other people
> helping you narrowing down the issue.
>
>
Certainly!

The dom0 is 4.18.6.  It is a custom-built version of the
linux-image-4.18.6, with xen_pciback compiled-in (instead of being a
module.)

The domU kernels are whatever on the CD-ROMs images. The host is shut down
at the moment, but I can get those tonight or tomorrow if it's really
important.

However, I disagree with andyhhp's assessment with regard to 32-bit/64-bit
protocols: these are virtual CD-ROMs, which are not PV block devices, but
fully-emulated hardware.
They speak the ATAPI protocol, which does not change based on the bitness
of the kernel running inside the VM.
The failure is happening when the domU kernel sends an IDENTIFY DEVICE
command to find out what type of drive it is.  Since that doesn't involve
anything in dom0 (optical drives exist separately and independently from
the media inside the drives), the dom0 kernel shouldn't be getting involved
at all.

(I would very much like more information on those 'interesting bugfixes'
that affect 32/64 compatibility, however.)

-- 
-- Stevie-O
Real programmers use COPY CON PROGRAM.EXE
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