Thank Jan and Roger, I may know how to add a new hypercall XEN_DOMCTL_gsi_permission, I will implement it in next version.
On 2024/1/9 18:46, Jan Beulich wrote: > On 09.01.2024 11:16, Chen, Jiqian wrote: >> On 2024/1/9 17:38, Jan Beulich wrote: >>> On 09.01.2024 09:18, Chen, Jiqian wrote: >>>> A new hypercall using for granting gsi? If so, how does the caller know to >>>> call which hypercall to grant permission, XEN_DOMCTL_irq_permission or >>>> that new hypercall? >>> >>> Either we add a feature indicator, or the caller simply tries the >>> new GSI interface first. >> I am still not sure how to use and implement it. >> Taking pci_add_dm_done as an example, for now its implementation is: >> pci_add_dm_done >> xc_physdev_map_pirq >> xc_domain_irq_permission(,,pirq,) >> XEN_DOMCTL_irq_permission >> >> And assume the new hypercall is XEN_DOMCTL_gsi_permission, do you mean: >> pci_add_dm_done >> xc_physdev_map_pirq >> ret = xc_domain_gsi_permission(,,gsi,) >> XEN_DOMCTL_gsi_permission >> if ( ret != 0 ) >> xc_domain_irq_permission(,,pirq,) >> XEN_DOMCTL_irq_permission > > No, falling back shouldn't be "blind". Fallback should only happen > when the new sub-op isn't implemented (hence why a feature indicator > may be necessary), and only if calling the existing sub-op promises > to be useful (which iirc would limit that to the PV Dom0 case). > >> But if so, I have a question that in XEN_DOMCTL_gsi_permission, when to fail >> and when to success? > > I'm afraid I don't understand the question. Behavior there isn't to > be fundamentally different from that for XEN_DOMCTL_irq_permission. > It's just that the incoming value is in another value space. > >> Or do you mean: >> pci_add_dm_done >> xc_physdev_map_pirq >> ret = xc_domain_irq_permission(,,pirq,) >> XEN_DOMCTL_irq_permission >> if ( ret != 0 ) >> xc_domain_gsi_permission(,,gsi,) >> XEN_DOMCTL_gsi_permission > > No, this looks the wrong way round. > >> And in XEN_DOMCTL_gsi_permission, as long as the current domain has the >> access of gsi, then granting gsi to caller should be successful. Right? > > I think so; see above. > > Jan -- Best regards, Jiqian Chen.
