On 2024/6/12 17:21, Jan Beulich wrote: > 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. Make sense. I will rebase the branch once your codes are merged.
> > Jan -- Best regards, Jiqian Chen.
