On 12.06.2024 11:07, Chen, Jiqian wrote: > On 2024/6/12 16:53, Jan Beulich wrote: >> On 12.06.2024 04:43, Chen, Jiqian wrote: >>> On 2024/6/10 23:58, Jan Beulich wrote: >>>> On 07.06.2024 10:11, Jiqian Chen wrote: >>>>> If run Xen with PVH dom0 and hvm domU, hvm will map a pirq for >>>>> a passthrough device by using gsi, see qemu code >>>>> xen_pt_realize->xc_physdev_map_pirq and libxl code >>>>> pci_add_dm_done->xc_physdev_map_pirq. Then xc_physdev_map_pirq >>>>> will call into Xen, but in hvm_physdev_op, PHYSDEVOP_map_pirq >>>>> is not allowed because currd is PVH dom0 and PVH has no >>>>> X86_EMU_USE_PIRQ flag, it will fail at has_pirq check. >>>>> >>>>> So, allow PHYSDEVOP_map_pirq when dom0 is PVH and also allow >>>>> PHYSDEVOP_unmap_pirq for the failed path to unmap pirq. And >>>>> add a new check to prevent self map when subject domain has no >>>>> PIRQ flag. >>>>> >>>>> Signed-off-by: Huang Rui <ray.hu...@amd.com> >>>>> Signed-off-by: Jiqian Chen <jiqian.c...@amd.com> >>>>> Reviewed-by: Stefano Stabellini <sstabell...@kernel.org> >>>> >>>> What's imo missing in the description is a clarification / justification of >>>> why it is going to be a good idea (or at least an acceptable one) to expose >>>> the concept of PIRQs to PVH. If I'm not mistaken that concept so far has >>>> been entirely a PV one. >>> I didn't want to expose the concept of PIRQs to PVH. >>> I did this patch is for HVM that use PIRQs, what I said in commit message >>> is HVM will map a pirq for gsi, not PVH. >>> For the original code, it checks " !has_pirq(currd)", but currd is PVH >>> dom0, so it failed. So I need to allow PHYSDEVOP_map_pirq >>> even currd has no PIRQs, but the subject domain has. >> >> But that's not what you're enforcing in do_physdev_op(). There you only >> prevent self-mapping. If I'm not mistaken all you need to do is drop the >> "d == current->domain" checks from those conditionals. > What I want is to allow PHYSDEVOP_map_pirq when currd doesn't have PIRQs, but > subject domain has. > Then I just add "break" in hvm_physdev_op without any checks, that will cause > self-mapping problems. > And in previous mail thread, you suggested me to prevent self-mapping when > subject domain doesn't have PIRQs. > So I added checks in do_physdev_op.
Self-mapping was a primary concern of mine. Yet why deal with only a subset of what needs preventing, when generalizing things actually can be done by having less code. Jan
