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.
> > Further see also > https://lists.xen.org/archives/html/xen-devel/2024-06/msg00540.html. > > Jan -- Best regards, Jiqian Chen.
