Re: [PATCH v2 05/27] include/hw/hyperv: Add MSHV ABI header definitions

[Magnus Kulke <magnuskulke@linux.microsoft.com>]

On Wed, Jul 02, 2025 at 11:11:41AM +0200, Cornelia Huck wrote:
> On Tue, Jul 01 2025, Magnus Kulke <magnuskulke@linux.microsoft.com> wrote:
> 
> > Introduce headers for the Microsoft Hypervisor (MSHV) userspace ABI,
> > including IOCTLs and structures used to interface with the hypervisor.
> >
> > These definitions are based on the upstream Linux MSHV interface and
> > will be used by the MSHV accelerator backend in later patches.
> >
> > Note that for the time being the header `linux-mshv.h` is also being
> > included to allow building on machines that do not ship the header yet.
> > The header will be available in kernel 6.15 (at the time of writing
> > we're at -rc6) we will probably drop it in later revisions of the
> > patch set.
> 
> The right way to handle header updates is to split the linux-header
> updates into a "dummy" update (that just adds the header) and replace
> that patch with a proper header update once the changes hit Linux
> mainline.
> 

Ah, that's right, the commit message is not accurate any more, I'll change
it in the next revision. The driver has been released as part of 6.15.

I was following Paolo's advice to include the headers in
`linux-headers/linux` and add an entry to
`scripts/update-linux-headers.sh`

https://lists.gnu.org/archive/html/qemu-devel/2025-05/msg04791.html

I might not have completely understood the process though, do you
suggest to run `update-linux-headers.sh` on a current kernel (the other
headers seem to be updated from 6.16-rc*, so I assume the latest rc?)
and include the resulting changes in a seperate commit?

> I have not looked at the contents of the series otherwise -- but if this
> is a system header (and not something that defines the kernel<->vmm
> interface), how do you make sure that your system has that installed?
> Maybe I'm misunderstanding.
> 

The kernel header does define the ioctls and ABI for the driver, albeit not
completely, some hyperv-specific types and defines are shipped as seperate
`include/hw/hyperv` header files.