Hi Andrew, On Fri, 8 Oct 2021, 20:07 Andrew Cooper, <andrew.coop...@citrix.com> wrote:
> On 06/10/2021 18:40, Rahul Singh wrote: > > Introduce XEN_DOMCTL_CDF_vpci flag to enable VPCI support in XEN. > > Reject the use of this new flag for x86 as VPCI is not supported for > > DOMU guests for x86. > > > > Signed-off-by: Rahul Singh <rahul.si...@arm.com> > > Reviewed-by: Stefano Stabellini <sstabell...@kernel.org> > > Acked-by: Christian Lindig <christian.lin...@citrix.com> > > I'm afraid this logic is broken. > > There's no matching feature to indicate to the toolstack whether > XEN_DOMCTL_CDF_vpci will be accepted or not. The usual way of doing > this is with a physinfo_cap field. > I am slightly puzzled by this. I am assuming you are referring to XENVER_get_features which AFAICT is a stable interface. So why should we use it to describe the presence of an unstable interface? > This flag needs using in Patch 10 to reject attempts to create a VM with > devices when passthrough support is unavailable. > May I ask why we can't rely on the hypervisor to reject the flag when suitable? > Ian, for the 4.16 release, this series either needs completing with the > additional flag implemented, or this patch needs reverting to avoid us > shipping a broken interface. I fail to see how the interface would be broken... Would you mind to describe a bit more what could go wrong with this interface? Cheers, > ~Andrew > >
