On 19/12/2023 1:48 pm, Mykyta Poturai wrote: > This patch adds the ability for the device emulator to inject MSI > interrupts into guests. This is done by adding a new DM op to the device > model library. > > It is not possible to reuse already existing inject_msi DM op, because > it does not have a devid parameter, which is required for translation of > MSIs to interrupt numbers on ARM.
Ok, so the original hypercall is broken. But the new hypercall isn't ARM specific. It's just better form of inject_msi, and needed for all architectures. So, name it DMOP_inject_msi2 and get rid of the ARM infix. > This approach was successfully tested on a virtio-pci setup with QEMU > backend emulating block devices with following changes from the mainline > Xen: > > This branch was taken as a base for virtio-pci: > https://github.com/xen-troops/xen/tree/xen-4.18-xt0.2 > > With added new VGICv3 from here: > https://github.com/Deedone/xen/tree/new_vgic_v2 > (although it should also work with the current VGIC) > > And patches from this branch to allow for proper ITS emulation in guests: > https://github.com/stewdk/xen/commits/pcie-passthrough-arm-vpci-v11 > > The main purpose of this RFC is to get some feedback on the addition of > the new DM op. Is it the right approach or should we somehow modify the > existing inject_msi DM op to be compatible with ARM? The DM_OP ABI does allow you to extend the structure behind DMOP_inject_msi, as long as 0 is meaningful. However, the semantics of zero-extending are wrong in this case, because it would mean that users of DMOP_inject_msi on an updated Xen would be sending interrupts with an implicit source id of host bridge. So you need a new DMOP_inject_msi2 that has better semantics. > diff --git a/xen/include/public/hvm/dm_op.h b/xen/include/public/hvm/dm_op.h > index fa98551914..a7d72e4389 100644 > --- a/xen/include/public/hvm/dm_op.h > +++ b/xen/include/public/hvm/dm_op.h > @@ -444,6 +444,15 @@ struct xen_dm_op_nr_vcpus { > }; > typedef struct xen_dm_op_nr_vcpus xen_dm_op_nr_vcpus_t; > > +#define XEN_DMOP_arm_inject_msi 21 > + > +struct xen_dm_op_arm_inject_msi { > + uint64_t addr; > + uint32_t data; > + uint32_t devid; uint32_t source_id; /* PCI SBDF */ Technically the PCI spec calls it the Requester ID, but Source ID is the more common name. It is important not to use "devid" because that implies it's only a 3 bit number, and it isn't. ~Andrew
