On Tue, Oct 12, 2021 at 12:38:35PM +0200, Michal Orzel wrote: > Hi Roger, > > On 11.10.2021 11:27, Roger Pau Monné wrote: > > On Wed, Oct 06, 2021 at 06:40:33PM +0100, 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. > > > > I don't like this approach, XEN_DOMCTL_CDF_vpci should be set for x86 > > PVH dom0, like we do for any other CDF flags when Xen builds dom0. > > > > Things like PVH vs PV get translated into CDF flags by create_dom0, > > and processed normally by the sanitise_domain_config logic, vPCI > > should be handled that way. > > > > Do you think you could see about fixing this? > > > > Thanks, Roger. > > > > I have one question about this fix. > If I set XEN_DOMCTL_CDF_vpci for dom0 pvh in create_dom0, then in > sanitise_domain_config or arch_sanitise_domain_config I have no > knowledge on whether I am dom0 or not. I can check if I'm PVH but not if dom0. > This would be needed to add a warning if this flag is set but we are not dom0 > pvh. > > Any ideas?
I've just realized this is more wrong that I thought. vPCI is signaled on x86 in xen_arch_domainconfig.emulation_flags, so introducing a top level option for it without removing the arch specific one is wrong, as then on x86 we have a duplicated option. Then I'm also not sure whether we want to move it from emulation_flags, it seems like the more natural place for it to live on x86. If we really want to make vPCI a CDF option we must deal with the removal of XEN_X86_EMU_VPCI, or else you could introduce an arch specific flag for vPCI on Arm. Thanks, Roger.
